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: INSIDE ATARI DOS

From The Editor's of COMPUTE! Magazine and
Optimized Systems Software, inc.

INSIDE
ATARI DOS

Compiled by Bill Wilkinson,
Optimized Systems Software, Inc.

Published by COMPUTE! Books,

A Division of Small System Services, Inc.,
Greensboro, North Carolina

ATARI is o registered trademark of Atari, Inc.

Preface

This book contains the only complete and official listings for the disk
File Manager System (FMS) commonly known as "Atari DOS 2. OS."
You will note that we have clearly stated that the purchase of this
book does not entitle you to make, sell, give, or otherwise distribute
copies of either the original Atari DOS 2. OS or any modified version
you may produce as a result of using this book.

By way of information, should you desire to produce and distribute
a modified version of this product (e.g., to support a new disk drive),
you must sign a contract and licensing agreement with the party who
owns the rights to grant such licenses for non-exclusive uses. Currently,
Optimized Systems Software is the only entity able to grant such
licenses.

Some of you may find it strange that the publishers of COMPUTE!
mai'azine are publishing this book. You might wonder why Atari,
Inc. , hasn't released this information before. Why can you only obtain
distribution rights from Optimized Systems Software? For the answers
to these and other questions we present the following Introduction,
an Inistorical perspective on the development of the systems software
for the Atari Home Computers.

All reasonable care has been taken in the writing, testing, and correcting of the text and of the
sottv'are within this book. There is, however, no expressed or implied warranty of any kind fVom
the authors or pubUshers with respect to the text or software herein contained. In the event of
any damages resulting from the use of the text or the software in this book, the authors or
publishers shall be m no sense liable. Please review the important cautions noted in Appendix A
regarding the use of this book.

Copyright © 1978, 1979, 1980, 1982 program listings. Optimized Systems Software, Inc.
AH rights reserved. Reproduction or translation of any part of this work beyond that permitted
by sections 1 07 and 1 08 of the United States Copyright Act without the permission of the '
copyright owner is unlawful.

Printed in the United States of America

ISBM 0-942386-02-7

10 98765432

Table of Contents

Preface Page ii

Introduction; Being a History of Two Births: "Coleen" and "Candy" Page iv

Chapter One: Atari DOS Overview Page 1

Chapter Two: Disk Organization Page 10

Chapter Three: FMS File Control Blocks (FOB) Page 15

Chapter Four: FMS Initialization Page 17

Chapter Five: FMS Entry Page 22

Chapter Six: FMS Exit Page 23

Chapter Seven: Device Dependent Commands Page 25

Chapter Eight: FMS Open Routines Page 3 1

Chapter Nine: FMS Close Routines Page 34

Chapter Ten: The GET BYTE Routine Page 36

Chapter Eleven: The PUT BYTE Routine Page 37

Chapter Tweh^e: Burst I/O Page 38

Chapter Thirteen: Reading the Directory as a File Page 40

Chapter Fourteen: Sector I/O Routines Page 42

Chapter Fifteen: File Name Decode Routine Page 46

Chapter Sixteen: Directory Searching Page 48

Chapter Seventeen: Write Next Sector Page 50

Chapter Eighteen: Read Next Sector Page 51

Chapter Nineteen: Get and Free Sector Routines Page 53

Chapter Twenty: The Boot Process Page 55

Chapter Twenty-One: Maintaining the Boot Record Page 57

Atari DOS 2. OS Page 59

Appendix A: An Intermediate User's Guide To This Book .... Page 102

COMPUTE! Books is a division of Small System Services, Inc.,

Puhlisliers of COMPUTE! Magazine

Editorial Offices are located at:

625 Fulton Street, Greensboro, NC 27403 USA. (919)275-9809

Optimized Systems Software, Inc. , is located at:

10379 Lansdale Avenue, Cupertino, CA 95014 USA. (408)446-3099.

Introduction

BEING A
HISTORY OF
TWO BIRTHS

"COLEEN"

AND
"CANDY"

I don't know exactly when the concept of the Atari Computer was
developed within the corporate mind of Atari, Inc., nor do I know all
of the people responsible for nursing that concept into reality. The
following history covers the relationship with Atari, Inc., during the
evolution of the system software.

Sometime in early 1978, when the Atari 800 and 400 were still
called "Coleen" and "Candy" and were still in the breadboard stages.
Atari bought a copy of the source for Microsoft 8K BASIC. This
version of BASIC was fundamentally the same product that was
implemented by Commodore in the early PETs, was used by OSI, and
was a close ancestor of Applesoft. Six months and many, many Atari
man-hours later, that 8K BASIC was almost functioning properly on
the Atari prototypes. But buying source for a program buys you just
that: source. Generally, you also receive little documentation,
sometimes obscure code, no guide to modification, and no real support.
What to do? The products were due to be shown in early January,
1979, at the Consumer Electronics Show (CES) in Las Vegas,
Nevada.

Enter Shepardson Microsystems, Inc. (SMI), my employer at
that time. Though little known by the microcomputer pukic, SMI
had already produced some very successful, private labeled
microcomputer software. Among our better-known efforts were the
original Apple DOS, Cromemco 16K Extended BASIC, and

Cromemco 32K Structured BASIC (just being completed at that
time). Also, we had done some work for Atari on a custom game
processor. (Which used a 12-bit ROM and 5-bit RAM configuration
and was well received at Atari, but never produced.)

Coincidentally, about that same time SMI had also purchased
source for Microsoft 6502 BASIC. After producing Apple's DOS, we
had the bright idea of mating the Apple II peripheral bus with the
KIM/SYM/AIM system bus (and it still seems like a good idea to us,
but ...). The idea was to provide a disk system (Apple's) to the Single
Board Computer market. Needing a BASIC to sell with the system,
we plunked down a few grand and purchased Microsoft's. Though it
looked to us like it would be difficult to modify, we were intending to
resell it with a minimum of changes, so it seemed appropriate.

A New BASIC?

Re-enter Atari, some time in the late summer of 1978, asking if SMI
could help them. With Microsoft BASIC? Well ... we really didn't
want to, but ... Could we propose a new BASIC? We talked. And
had meetings, and a study contract, and more meetings, and finally
we wrote a specification for a lOK, ROM-based BASIC. (I still have a
copy of that spec, and it's amazing how little the final version deviated
from that original.)

Of course, in the middle of all these discussions, Atari naturally
divulged how their (truly superb) ROM-based Operating System
would interface both with BASIC and with various devices.
Somewhere in here, my memory of the sequence of events and
discussions becomes a little unclear, but suffice it to say that we found
ourselves making a bid on producing not only a BASIC for Atari, but
also the File Manager (disk device driver) which would change Atari
OS to Atari DOS.

Sometime in late September, 1978, the final proposal was made
to Atari, and it was accepted by them shortly thereafter. In mid-
October, 1978, we received the go-ahead. The project leader was Paul
Laughton, author of Apple DOS. The bulk of the work ended up
being done by Paul and Kathleen O'Brien. Though I was still involved
in the finishing touches on Cromemco BAcSIC, I take credit for
designing the floating point scheme used in Atari BASIC. Paul Krasno
implemented the math library routines following guidelines supplied
to us by Fred Ruckdeschel (author of the acclaimed text, BASIC
Scientific Subroutines). And, of course, much credit must go to Mike
Peters, our combination keypuncher/computer operator/junior
programmer/troubleshooter.

Since we obviously couldn't have the Atari machines to work on
(they hadn't been built yet), the first step was to bring up an emulator
for Atari's CIO ("Central Input-Output," the true heart of Atari's
OS) on our Apple II systems. With Paul Laughton leading the way
(and doing a lion's share of the work), the pieces fell together quickly.
"Little" things had to be overcome: the cross-assembler was modified
to handle the syntax table pseudo-ops, the 256-byte Apple disk sectors
had to be made to look like 128-byte Atari sectors, the BASIC
interpreter seemed to function, but was waiting for the floating point
routines. And there are funny things to tell of, also. Like our cross-
assembler, running on an IMP-16P (a 1973 vintage, 16-bit, bit-sliced
PMOS microprocessor) that used keypunched cards for input, a floppy
disk (with no DOS) as temporary storage, and a paper tape punch as
output.

Somehow, Kathleen and Paul guided the two programs unerringly
toward completion. On December 28, 1978, Atari's purchasing
dej^artment at last delivered a signed copy of the final purchase order.
It called for delivery of both products by April 6, 1979. There was a
clause which provided for a $1,000 per week incentive (if we finished
early) and penalty (if we finished late). What is especially humorous
about that December 28th date is that the first working versions of
both BASIC and FMS had already been delivered to Atari over a week
before! That is fast work.

Fortunately, then. Atari took their new Atari BASIC to CES.
Unfortunately, there was a limit on the amount of incentive money
collectible. Oh, well.

In the months that followed, SMI fixed bugs, proofread manuals,
and worked on other projects (including the Atari Assembler/Editor,
which was mostly Kathleen's effort). The nastiest bugs in BASIC were
fixed by December, 1979, but it was too late: Atari had already
ordered tens of thousands of BASIC ROMs. The FMS bugs were
easier to get fixed, since DOS is distributed on disk.

In mid- 1980, Paul Laughton once again tore into FMS. This
tiir.e, he modified it to handle the ill-fated 815 double-density disk
drive and added "burst I/O" (and there will be much more about both
these subjects in the technical discussion that follows).

In late 1980, and early 1981, Bob Shepardson, owner of
Shepardson Microsystems, Inc. , decided that the pain and trouble of
having employees wasn't justified by the amount of extra income (if
any) that he derived. Though we still occasionally function in a loose,
cooperative arrangement, the halcyon days of SMI seem to be over.

A New Beginning

I negotiated with Bob Shepardson for his rights to the Atari products
(FMS, BASIC, and the Assembler/Editor) and their Apple II
counterparts. Thankfully, Atari had purchased from SMI only a non-
exclusive right to distribute these products. SMI had retained the
rights to license other users on a similar non-exclusive basis (and,
indeed, SMI sold a version for the Apple II during most of 1980).

So now it was frantic time again: this was February 25, 1981, and
the West Coast Computer Faire was April 3rd. But our brand new
company. Optimized Systems Software, arrived on time, bringing
with it BASIC A+ , OS/A+ and EASMD. All three were enhanced,
disk-based versions of the original Atari programs (and, in fact, derived
some of their enhancements from the previous OSS Apple II
products) .

The products have been well received by the Atari user
community, in part due to the fact that they are truly compatible, yet
enhanced, versions of standard Atari software.

Wily This Booic?

The decision to publish these listings was not an easy one to make;
and it is, in its own way, an historic occasion. After all, have you ever
seen anyone offering source or listings of CP/M, the most popular of
all computer operating systems? Since Atari, to their credit, has
hcinored the original agreement with SMI and not released either
source or listings without permission, the responsibility for doing so
seemed to rest with OSS.

But Atari has set a powerful precedent by publishing the listings
of DUP (their portion of DOS 2. OS) and the OS ROMs. The clamor
from Atari users for the source for FMS finally even reached us, so we
hsve bowed to the inevitable, and honored the same commitment
that Atari has made: to release as much information and aid as possible
to the user community.

We hope that the users will appreciate these efforts and, in turn,
respect our rights and Copyrights. As long as there is a mutual respect
and benefit, you, the user, can expect continued support.

AI>out Ihis Booic

^X'ith the release of this book, the dedicated Atari enthusiast can
e>:amine all the inner workings of Atari DOS and modify his (or her)
system to his heart's delight. Rather than simply publish listings, we
have chosen also to provide a complete guide to the workings of FMS.
Although the listing itself is relatively clear and commented, all

but the most expert would have trouble plowing through some of the
toniuous logic necessary in such a program. The guide included here
describes all aspects of the FMS, including the external view, the
chsitts and tables, the various interfaces, and (in copious detail) the
functions of the individual subroutines (including complete entry and
exit parameters).

There is much of value here even for the person who never
intends to modify Atari DOS. We feel that FMS is a fairly well-
structured, relatively sophisticated, system level assembly language
program. We hope that most users will gain by the insights presented
here.

We would welcome any notes you would care to send pointing
out errors either in the DOS or in this book.

Bill Wilkinson
Optimized Systems Software
Cupertino, California
February, 1982

Chapter One

ATARI
OVERVIEW

The standard Atari Disk Operating System, DOS 2.08, consists of
four separate elements, ranked as follows in order of their "visibility"
to the average DOS user.

1. DUP - Disk Utility Package

2. CIO - Central Input/Output

3. FMS — File Management System

4. SIO - Serial Input/Output

It is helpful to understand the entire Input/Output (I/O) process.
While this book is intended to give detailed information on the
workings of FMS, this overview will attempt to at least show how the
four elements of DOS are connected. To this end, we would first call
your attention to Figure 1. This figure is, itself, an overview of the
entire Atari I/O system, including indications as to how and where
data and control flows between the various elements thereof. Figures
1-1 through 1-4 show "close-ups" of portions of this diagram as they
re .ate to the four elements of EXDS.

In these figures, the rectangular boxes represent system elements,
and are appropriately labeled. The wide, lettered arrows represent the
flow of data (via buffers, control blocks, or even registers) between
the various elements. The narrow, numbered arrows show how and
where control, and control information, is transferred.

1-1. Disk Utility Pacicage

DUP (which shows as "DUP. SYS" in a disk directory listing) is the
most obvious and visible element of Atari EXDS. DUP's function is to
provide the user with keyboard access to the various file management
functions in FMS. It does so via the menu which is displayed when,
for example, the user keys "DOS" from BASIC. Actually, the menu
offers several options which are not directly a part of the FMS (e.g. ,
copy and duplicate files). Refer to the Atari Disk Operating System U

CHAPTER ONE

Reference Manual (part number C016347) for more information.

DUP is not an integral part of FMS. DUP may be relatively easily
replaced with a program of the user's choice. In fact, our own OS/A +
does exactly that: instead of a menu, the user is given a command-
driven keyboard interface to the other elements of DOS.

DUP is not even a privileged portion of IX)S (excepting, perhaps,
for reeding to know a little of the internals of FMS when it performs a
Duplicate Disk function). Any user application program (and that
includes Atari BASIC, BASIC A + , EASMD, and many, many
more) interacts the same way DUP does. Figure 1-1 shows the "proper"
flow of control in EXDS. Note that DUP transfers control only to
CIO, which, in turn, transfers control to FMS and thence to SIO. An
application program which maintains this protocol should be able to
perform correctly in any Atari system, regardless of the revision of the
OS ROMs and/or FMS.

Of course, control is not the only thing which DUP must transfer.
It must also tell CIO where its data is and what to do with it. Refer to
Figure 1-2 for a diagram of the complete application/CIO interface
(again, it is labeled in this way because DUP is just another application
program as far as the rest of DOS is concerned). CIO always expects
an Input/Output Control Block (lOCB) and usually (i.e., for all but
the simplest operations) needs a buffer into or out of which it may
perform its operations.

1-2. Central Input/Output

CIO is actually the heart of the entire Atari Computer. It is less than
800 bytes long and yet serves to handle virtually all the input and
output which takes place in the computer. CIO is a part of the Atari
"OS ROMs," the I OK byte package which also houses the floating
point routines, the default character set, the interrupt handlers, and
several device drivers.

The entire set of operations summarized in Figure 1-2 is covered
in detail in the Atari OS Manual (C01655) and will be covered only
briefly here. Readers of COMPUTE! will also find some helpful material
on this subject in issues #18 through #21 (November, 1981, through
February, 1982) in the "INSIGHT: ATARI" columns.

In order to allow easy control and data flow, CIO is written to
expect and provide for eight Input/Output Control Blocks (lOCBs)
which are used to pass the information needed to process the various
kinds of I/O requests. An application places the necessary command
and control information in an lOCB which it selects (data path A). If
a buffer is required, the application must provide one (data path C)

CHAPTER ONE

and place its address into the lOCB. When ready to execute the I/O
command, the appUcation places the lOCB number (times 16) in the
6502's X-register (data path C) and executes a JSR call to CIO (control
path 1 ). Note that a few command variations may pass data via the
6502's A-register, but we may consider that simply a special case
location of the user's buffer.

When CIO receives control, it examines the information in the
lOCB (and, for some operations, in the user buffer) to determine
what actions it is to perform. Generally, this action requires the
execution of a device handler routine.

A device handler (interchangeably known as a device driver) is a
system routine that performs I/O operations for a specific device (or
class of devices). Examples of device handlers include the "P:" driver
(the printer) and the "E:" driver (the screen/keyboard editor). Figure
1-3 illustrates the interface between CIO and the various device
handlers. Note that FMS is simply another device handler as far as
CIO is concerned, having been given the name "D:".

All device drivers are required to contain a table of address pointers
(known as the Device Vector Table) to various specific routines
within themselves, including a device OPEN routine, GET
CHARACTER routine, etc. The name of a device and the address of
this table is placed in CIO's Device Handler Table. When an
application program makes an I/O request to CIO for a specific device,
CIO searches the Device Handler Table for the given name and
corresponding Device Vector Table address. With the thus-located
vector table, CIO can then call the appropriate device handler routine
(via a JSR, along control path two of Figure 1-3).

1-3. File Management System

As. stated above, FMS is actually simply another device driver as far as
CIO is concerned. The control and data flows shown in Figure 1-3 are
equally valid for all device drivers in the Atari system. Note that
many of the drivers in the default ("as-shipped") system reside entirely
within the so-called OS ROMs. Although it resides in RAM, what is
somewhat unique about FMS is that the Atari system initialization
code contains a segment of "boot" code which loads FMS into memory
upon power-on.

FMS is the system device handler for all I/O operations that
specify the device name "D" (including "Dl:", "D2:", etc.). In order
to perform its functions, FMS examines the data in the specified
ICCB (data path F). It may also examine, read, or write data to or
frcim the user-supplied buffer (data path I). Data path H is used to pass

CHAPTER ONE

the I(ZXZ!B-designator (again, via the X-register) and single-byte transfer
data (via the A-register).

FMS is called upon to perform a variety of tasks, including all
disk I/O, file renaming, protecting, deleting, etc. Since the rest of
this book consists of a listing of FMS along with detailed explanations
of all sections thereof, we will not now dwell on the inner workings of
FMS.

However, we do need to note that, in order to perform its work,
FMS must transfer data to and from the disk. FMS accesses the disk
drive via SIO, the fourth element of DOS.

1-4. Serial Input/Output

SIO is the name given to the component of DOS which drives and
controls the Atari serial I/O bus and the various peripherals (disk,
printer, modem, etc.) which are placed on that bus. Figure 1-4
illustrates the interface between FMS and SIO, but it could just as
well serve to show (for example) how the printer driver talks to the
various Atari printers.

The SIO is primarily driven by a request placed in SIO's Device
Control Block (DCB) by the device handler (data path K) followed
by a transfer of control (control path three) via a JSR. SIO uses the
information in the DCB (data path M) to determine what it needs to
do. If the EXHB specifies a serial bus data transfer (as opposed to, for
example, a status request), then the address of the data buffer must
also be passed (via a field in the DCB). For example, the FMS buffer
shown is accessed via data paths J (from FMS) and L (from SIO).

Although SIO only understands the single system DCB, the
buffer specified may be located anywhere in memory. FMS takes
advantage of this to implement "burst I/O" (discussed in section 12),
which has SIO transferring data directly to or from the user's buffer
(data path E).

Since the actual disk data transfer occurs in fact within the 810
disk drive and, since SIO communicates to the drive via data path N,
one might reasonably argue that the disk drive constitutes a fifth
component of DOS. However, because the disk drive functions are
preprogrammed in ROM, and because SIO implements the only
method of accessing the disk (as well as most other peripherals), then,
for all practical purposes, even machine language software may treat
SIO as the last link in the I/O chain on the Atari Computers.

Once again, we remind you to study Figure 1. In the following
dissertation and dissection of FMS, we shall refer to this chart often.

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Chapter Two

DISK
ORGANIZATION

The purpose of FMS is to organize the 720 data sectors available on an
810 (diskette into a system of named data files. FMS has three primary
data structures that it uses to organize the disk: the Volume Table of
Contents, the Directory, and Data Sectors. The Volume Table of
Concents is a single disk sector which keeps track of which disk sectors
are available for use in data files. The Directory consists of directory
sectors. It is used to associate file names with the location of the files'
sectors on the disk. Each Directory entry contains a file name, a
pointer to the first data sector in the file, and some miscellaneous
information. The Data sectors contain the actual data and some
control information that link one data sector to the next data sector
in the file. Figure 2-1 illustrates the relation between the Directory
and the Data files.

Disk Directory

The Directory starts at disk sector $169 and continues for eight
contiguous sectors, ending with sector $170. These sectors were
chos(m for the directory because they are in the center of the disk and
therefore have the minimum average seek time from any place else on
the disk. Each directory sector has space for eight file entries. Thus, it
is possible to have up to 64 files on one disk.

A Directory entry is 16 bytes in size, as illustrated by Figure 2-2.
The directory entry flag field gives specific status information about
the current entry. The directory count field is used to store the number
of sectors currently used by the file. The last eleven bytes of the entry
are the actual file name. The primary name is left justified in the
primary name field. The name extension is left justified in the extension
field. Unused filename characters are blanks ($20). The Start Sector
Number field points to the first sector of the data file.

Data Sectors

A Data Sector is used to contain the file's data bytes. Each 128 byte
data sector is organized to hold 125 bytes of data and three bytes of

CHAPTER TWO

control information as shown in Figure 2-3. The data bytes start with
the first byte (byte 0) in the sector and run contiguously up to, and
including, byte 124. The control information starts at byte 125.

The sector byte count is contained in byte 125. This value is the
actual number of data bytes in this particular sector. The value may
range from zero (no data) to 125 (a full sector). Any data sector in a
file may be a short sector (contain less than 125 data bytes).

The left six bits of byte 126 contain the file number of the file.
This number corresponds to the location of the file's entry in the
Directory. Directory entry zero in Directory sector $169 has the file
number of zero. Entry one in Directory sector $169 has the file number
one — and so forth. The file number value may range from zero to 63
($3F). The file number is used to insure that the sectors of one file do
not get mixed up with the sectors of another file.

The right two bits of byte 126 (and all eight bits of byte 127) are
used to point to the next data sector in the file. The ten bit number
contains the actual disk sector number of the next sector. Its value
ranges from zero to 719 ($2CF). If the value is zero, then there are no
more sectors in the file sector chain. The last sector in the file sector
chain is the End-Of-File sector. The End-Of-File sector may or may
not contain data, depending upon the value of the sector byte count
field.

Volume Table Of Contents (VTOC)

The VTOC sector is used to keep track of which disk sectors are
available for data file usage. The VTOC sector is located at sector
$16'8. Figure 2-4 illustrates the organization of the VTOC sector. The
most important part of the VTOC is the sector bit map.

The sector bit map is a contiguous string of 90 bytes, each of
which contains eight bits. There are a total of 720 (90 x 8) bits in the
bit map - one for each possible sector on an 810 diskette. The 90
bytes of bit map start at VTOC byte ten ($0A). The leftmost bit ($80
bit) of byte $0A represents sector zero. The bit just to the right of the
leftmost bit ($40 bit) represents sector one. The rightmost bit (bit
$01 ) of byte $63 represents sector 719.

The fact that EMS interprets the bit map as representing sectors
zero through 719 is a bug. The Atari 810 disk drive will not accept
commands for sector zero. It will accept commands for sector 720. In
other words, the bit map is skewed by one. The problem cannot be
fix€:d now because there are already tens of thousands of diskettes
whose bit maps are to be interpreted as representing sectors zero through
719, and because some savvy applications writers have taken advantage

CFUVPTER TWO

of this feature. (A bug which generates useful side effects is known in
the programming profession as a feature. ) Sector 720 can never be
use(i by FMS and is therefore available for miscellaneous purposes.

Directory Sectors
Sector $169 -

Figure 2-1

CHAPTER TWO

Typical Directory Sector

Er^tryO

Entry!

Entry 2

Entry 3

Entry 4

Entry 5

Entry 6

Entry?

Typical Directory Entry

Count

SSN

Primary Nome

Extension

Start Sector Number (Low, Higti)
The Sector Number of ttie First
Sector in the File Sector Chain

Count (Low, High)
The Number of Sectors in the File

Flag
$00 - Entry Has Never Been Used
$80 - Entry Has Been Deleted
$40 - Entry In Use
$20 - Entry Locked
$02 - File Created By DOS 2
$01 - File Opened For Output

Figure 2-2

CHAPTER TWO

Typical Data Sector

Data
125 Bytes

Control

Byt€i 125
Byt6i 126

Byt€i 127

1 \-^

■r

V ^

1 • k-^

Number Bytes Used In Sector (0-125)
Next Sector Number (Might Two Bits]
File Number (0-63)
Next Sector Number (Low Eight Bits)

Figur€J 2-3
VrOC Sector ($168)

0-9
Misc. info.

$0A-$63

Sector Usage
Bit Map

$64-$7F
Unused

1
3
5
6

1 1 1

Type Code ( = in DOS 2.0)
Number Sectors Total ($2C3)
Number Unused Sectors
Reserved
Unused

- Eacti bit represents a specific sector

- Thie left most bit ($80) of byte $0A is sector number (does not exist)

- Thie next bit ($40) of byte $0A is sector number 1

- The right most bit ($01) of byte $63 is sector number $719.

- If the bit is one, the sector is unused and available

- If the bit is off (zero), the sector is used

Figure 2-4

Chapter Three

FMS

FILE CONTROL

BLOCKS

(FOB)

The FMS File Control Blocks are used to store information about files
that are currently being processed. Each file that is being processed
concurrently by FMS requires one FCB. Since the Atari system has
eight lOCB's, FMS must be prepared to handle up to eight files
concurrently, thus there are eight FCBs. The FCBs were designed to
have a one-to-one correspondence with the lOCBs. When a file is to
be processed with ICXI^B number three, FMS will use FCB number
three for that file. When a file is to be processed with lOCB number
five, FMS will use FCB number five for that file. Each FCB is the
same size as an lOCB (16 bytes). The FCBs are located in a contiguous
RjKM area just like the lOCBs. When CIO calls FMS, the X register
contains the displacement (ICXDB number times 16) to the lOCB
making the request. The FMS uses this displacement value to access
both the lOCB information and the FCB information. Please refer to
the listing at location $1381 for the following discussion about the

fc:bs.

FCBFNO

The file number of the file currently being processed. The value (zero
to 63) is shifted left two bits. When a file has been opened for reading,
this value will be used to check for a file number mismatch in the data
se<:tors. When a file is opened for write, this value will be placed in
the file number field of the data sectors.

FCBOTC

0]3en Type Code. This value is used as a flag to indicate which mode
the file has been opened for:

Input is $04.

CHAPTER THREE

Output is $08.
Update is $0C.
Append is $01.
Directory read is $02.

FCBSLT

This is a tlag used to indicate that the file being processed was created
by EOS 1 rather than OOS 2. The Data Sector length byte has a
different interpretation under DOS 1 .

FCBFLG

This field is a working flag. If the value is $80, then the file is eligible
to ac:quire new data sectors. Files that are opened for Output or Append
are e'ligible to acquire new data sectors. If the value is $40, then the
sector currently is in a memory buffer, has been modified, and needs
to b<; written back to the disk.

FC»MNL

If the file is opened for Output or Append, this value will be either
125 or 253 depending upon the drive type. The 253 value is meant for
the i\tari 815 dual density drive. If the file is opened for Read or
Update, then this value represents the number of data bytes that are
in the data sector currently in a buffer. This value is obtained from the
Data Sector data length field (byte 125 of the data sector.)

FCBDLN

This value points to the next data byte to be operated on in a data
sector. If the file is opened for Output or Append, this value points to
the next available (unused) data byte in the current data sector. If the
file is opened for Update, then this value points to the next data
sector byte to be either read or modified. If the file is opened for
Inptit, then this value points to the next byte to be read.

FCBBUF

This value is an index into the sector buffer table. The sector buffer
table is a list of buffer addresses. When a file is being processed, a
sector buffer is required to hold data sectors. This field tells FMS
which FMS buffer has been allocated to the file.

FCBCSN

The sector number of the sector currently in the buffer is stored in this
field.

FCBLSN

The sector number of the next sector in the file chain is stored in this
field.

FCBSSN

If the file has been Opened for Append, then this field contains the
sector number of the start of the sectors to be appended to the file
when the append file is closed.

Chapter Four

FMS
INITIALIZATION

DUP gets control whenever the system is booted or the RESET key is
pressed. DUP will call the FMS initialization routine, DINIT at $7E0.

DINIT

Functions:

1) Determine how many (and what type of) disk drives will be
used.

2) Set up a drive table and allocate a drive buffer for each drive.

3) Allocate sector buffers and build the sector buffer table.

4) Clear the FCBs to zero.

5) Set MEMLO.

6) Enter the D: device into the Device Handler Table.

7) Exit to caller via RTS.

Drive Determination

Th<; DRVBYT byte at $70A is used to tell FMS how many disk drives
will be used and what the drive number of the drives will be. The

CHAPTER FOUR

rightmost bit (bit $01) indicates drive 1. The next left bit ($02)
indicated drive 2 - and so forth. If the bit is one, then the drive is to
be used. If the drive is zero then the drive is not to be used. The code
will allocate up the eight drives, even though the 810 hardware only
has switches for drives 1,2,3 and 4.

If DRVBYT indicates that a drive is to be used, then FMS issues
a status command to that drive to determine if it is active and what
type (810 or 815) of drive it is.

Drive Allocations

The drive determination process sets up two tables (Figure 4-1). The
first table is the DRVTBL. This table is indexed into by the drive
number (minus one). If the value in the table is zero then the drive is
not to be used. If the value is one, then the drive is an active 810 and
requires one drive buffer. If the value is two, then the drive is an 815
and requires two 128 byte buffers.

The second table is the drive buffer table. The drive buffer table
contains the address of the drive buffer to be used for each drive. This
Drive Buffer will be used to hold the VTOC sector on the diskette in
the drive. The table is separated into two sections: DBUFAL contains
the least significant address byte and DBUFAH which contains the
most significant address byte. The drive buffer table is also accessed by
the drive number (minus one).

When a file is being processed, the Drive number is obtained
froiTi the lOCB Device Number field, ICDNO. The obtained value is
decxemented by one and is then used as an index into the Drive Tables.
The Drive Type is copied from the DRVTBL entry to DRVTYP
($1 2FE) for easy access by FMS. The Drive Buffer address is copied
from the DBUFAL and DBUFAH table entries to the zero page drive
buffer pointer, ZDRVA ($45).

Sector Buffer Allocations

The SABYTE at location $709 is used to inform FMS about the
number of 128 areas to be allocated as sector buffers. One 128 buffer is
required for each file which is to be processed concurrently on 810
drives. Two 128 byte buffers are required for each file which is to be
processed concurrently on 815 drives.

The Sector Buffer Allocation table, SECTBL at $1319, is used to
indicate if a buffer is available for allocation to a file (Figure 4-2). If a
buffer is available, the entry is set to zero. If the buffer is not available,
the entry is a minus value. The table is 16 bytes in size and therefore
cari be used to allocate up to sixteen 128 byte buffers. During the

CHAPTER FOUR

initialization process, entries which are to be unused are set to a minus
value.

The Sector Buffer Address Table is a table of addresses which
point to the individual sector buffers. The table is divided into two
parts: SABUFL contains the least significant address byte, SABUFH
contains the most significant address byte.

When a file is being processed, an available buffer number is
found in SECTBL by search for a zero valued entry. The located
buffer is allocated to the file by entering a minus value ($80) into the
table and placing the corresponding buffer number into the DCB
buffer number field, FCBBUF. When the file processing is done, the
buffer is deallocated by setting the SECTBL entry to zero.

Setting MEMLO

The Atari MEMLO location ($2E7) is set after the FMS buffers have
be4;n allocated. The address of the last sector buffer allocated is
incremented by 128. This value is then placed into MEMLO.

Dcivice Handler Table Entry

The Device Handler Table ($31 A) is searched for a "D" entry or the
first (from the top) empty entry. When an appropriate entry is found,
FVIS inserts (or reenters) "D" as a DEVICE NAME and sets the
DEVICE vector entry to point to the FMS Device Vector table at
DFMSDH ($7CB).

CHAPTER FOUR

$70A DRVBYT .BYTE $0F ; Allocates Drive 1,2,3,4

Drive Bits

1111

S1311 DRVTBL

• + 9

Drive Table

Drive No.

Index

-••3

Drive Type From Status

810 Drive -m

810 Drive •«

815 Drive -•

815 Drive ■•

No Drive
No Drive
No Drive
No Drive

[1;1329 DBUFAL

• + 8 : Drive Butter Address Table (Lov>/) |

1331 DBUFAH

• + 8 : Drive Butter Address Table (High)

70C SASA

.WORD

$1A7C : Butter Start Address

Dr ive No.
1
2
-••3
4
5
6
7

Index
~0~

DBUFAH

DBUFAL

1A
1A

7C
FC

128 Byte Butter For Drive 1 At S1A7C
256 Byte Butter For Drive 3 At $1B7C

Figure 4-1

Drive Tables

CHAPTER FOUR

$1319 SECTBL

• + 16 ; Sector Allocation Table

Buffer Number

Buffer Is Available

00
00

Buffer Is Available

Buffer NOT Available

!;709 SABYTE BYTE

7 : Number Of 128 Byte Sector Buffers

S1339 SABUFL

• + 16 ; Sector Buffer Address (Low) Table

!)1349 SABUFH

• + 16 ; Sector Buffer Address (High) Table

(Last Drive Buffer Address + Dri\

/e Type (1 or 2) • 128)

Buffer Number SABUFL SABUFH

•• ■'

(Previous Entry + 128)

IE
1E

OC
80

Sector Buffer 4 Address = $1E80

Figure 4-2

Sector Allocation Tables

Chapter Five

FMS
ENTRY

The Device Vector Table for FMS is located at DFMSDH ($7CB).
The address of this table is placed in the Device Handler Table by the
FMS Initialization routine. When CIO needs to call an FMS function
(Figure 1, control path 2), it will locate the address of the function via
the' table at DFMSDH. This table is the standard Atari Device Handler
Vector Table. The six entries are for:

Open

Get Byte

Put Byte

Status

Device Dependent (XIO) Commands

Each of the six FMS entry points starts with a subroutine call to
the FMS SETUP routine. SETUP ($1164) prepares FMS parameters
to deal with the particular task to be performed.

SErup

Address -$1164

Entry Registers - A = Possible 'Put Data' data byte.
X = lOCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = lOCB number times 16.

Y = Sector Buffer Index.

Functions:

1) Initialize ERRNO to $9F. This value will be used in the FMS
exit routines to form a FMS error number in the event of error.

2) Save the X Register in CURFCB. This value will be used as
an index to the proper lOCB and the proper FCB for the current
operation.

3) Save the value of the stack register as it was upon entry to

FMS. This value will be used in the FMS exit routine.

4) Set up drive information values from the drive number
contained in the zero page lOCB field ICDNOZ.

5) Allocate a sector buffer to the FCB if one is not already
allocated.

Chapter Six

FMS
EXIT

There are two types of FMS exits: the normal exit and the error exits.
Both of these exit types end up calling the RETURN routine.

RETURN

Address -$12D3

Entry Registers — A = Return Code.
X = Don't Care.

Y = Don't Care.

Exit Registers — A = Possible 'Get Byte' data byte.
X = lOCB number times 16.

Y = Return Code.

Functions:

1 ) The X register is loaded with the current lOCB number times
16 from CURFCB.

2) The return code is placed in the ICXZ^B status field (ICSTA).

3) The stack register is restored to point to the stack displacement
at FMS entry from the value saved in ENTSTK.

4) The possible "Get Data" data byte is loaded into the A
register.

5) The Y register is loaded with the return code.

ClflAPTER SrX

6) The caller (CIO) is returned to via the RTS instruction.

eKEATAnd FGREAT

GP.EAT and FGREAT are the exit points used by FMS when the
operation has terminated normally. FGREAT is located at $12EA and
is used to free the sector buffer that has been allocated to the FCB.
The FRESBUF routine is used to free the buffer. FGREAT exits
directly to GREAT ($12F0). The GREAT exit point loads the normal
return code ($01) into the A register and goes to RETURN.

Error Exits

The ERREOF exit is called when an end of file condition is found.
ERREOF loads the end-of-file condition code ($88) in the A register
and goes to RETURN.

The ERRIO exit is called if an error occurs during an I/O operation
(Figure 1, control flow 3). The error code from the DCB (control
path K) is loaded into the A register as the FMS return code and
control is passed to RETURN.

All other errors exits are at the ERxxx labels starting at $12B5.
Th(; error code is developed by means of a series of 6502 INC
instructions which increment the ERRNO (which was initialized to
$9F at FMS entry). The final instruction at the end of the INC chain
loaiis the final ERRNO value into the A register and control is passed
directly to RETURN.

Chapter Seven

DEVICE

DEPENDENT

COMMANDS

A C'evice Dependent Command is any command which is not Open,
Close, Get Byte, Put Byte, or Status. When the command value in
the lOCB is greater than 15 ($0F), CIO will call the Device Handler
Device Dependent Command routine. The Device Handler must
det€;rmine if the command is a valid command for that device. The
Device Dependent Commands that for FMS are:

Rename

Delete

Lock

Unlock

Point

Note

Format

The FMS Device Dependent Command routine starts at
DFMDDC.

DFMDDC

Address - $BA7

Entry Registers - A = Don't Care.

X = lOCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = lOCB and FCB number times 16.

Y = Unknown.

Function:

1) Call SETUP

2) If the command is Format (254) , then go to the Format routine,
XFORMAT at $D18.

3) If the command is not Format, then check that the command

CHAPTER SEVEN

value is $20 through $26. If the command value is not in this
range then exit via the ERDVEXH (Command Error) routine.
4) If the command is valid, go to the command via the DCDCVT
vector table.

XFORMAT

The XFORMAT routine executes the FORMAT Device Dependent
Command.

Address -$D18

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) Issue the format I/O command to the drive. This will cause
the drive to perform the physical formating of the disk. If the
command returns with good status and there were no bad sectors
reported, then continue with the logical format operations. In
the event of physical format errors, exit via the ERDBAD error
exit.

2) Clear the drive buffer to zero.

3) Set the sector count values into the DVDMSN (VTOC
displacement one) and the DVDNSA (VTOC displacement
three) fields.

4) Set all 90 sector bit map bits to one (available).

5) Deallocate the first four sectors for the boot sectors.

6) Deallocate the middle nine sectors for the VTOC and the
Directory.

7) Write the VTOC to the Disk.

8) Clear the eight directory sectors to zero.

9) Exit via the FGREAT exit.

XDELETE

The XDELETE routine executes the DELETE Device Dependent
Command.

Address — $C3 2

Entry Registers - A = Don't Care.

CHAPTER SEVEN

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Parameters - A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1) The filename is decoded via the FNDCODE routine.

2) The first filename is searched for via the SFDIR routine.

3) The file, if found, is deleted via the XDELO routine.

4) If the file just deleted was DOS. SYS then the boot record is
re-written via the DELEXDS routine.

5) The directory is searched for the next matching entry. If an
entry is found then the process repeats at step three. If no further
matching directory entries are found, then exit via FGREAT.

XOELO

Tbe XDELO routine is used to delete the file whose directory entry is
indicated by the CDIRD (current Directory Displacement) byte

($1305).

Address - $C53

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) The OPVTOC routine is called to insure that the disk is not
write protected.

2) The TSTLCXZIK routine is called to insure that the file is not
locked.

3) The file deleted bit is set in the directory entry flag and the
directory sector is written back to the disk.

4) The VTOC sector bit map bits for the sectors in the file are
set to one to make them eligible for reuse. This process is achieved
by reading each sector in the file sector chain and calling the
FRESECT routine to change the VTOC bit map.

5) The VTOC Write Required Bit is set so that the VTOC will
be written back to the disk.

CI-IAPTER SEVEN

XRENAME

The XRENAME routine executes the RENAME Device Dependent
Command.

Address - $BD9

Entry Registers - A = Don't Care.

X = ICXDB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1) The filename is decoded via the FNDCODE routine.

2) The directory is searched for the first entry to be renamed. If
no entry is found then the ERFNF (File not found) exit is taken.

3) The TSTLOCK routine is called to insure that the file is not
locked.

4) If TSTDOS determines that the old filename is DOS. SYS
then the boot record is rewritten via the DELDOS routine.

5) If new filename is EXDS.SYS, then the boot record is rewritten
via the SETDOS routine.

6) The filename in the directory is changed to the new filename.

7) The directory sector is rewritten.

8) The directory is searched for the next filename match. If a
match is found, then the process repeats at step three. If no
further match is found then, exit via FGREAT.

XLOCKAndXUNLOCK

The XLOCK routine executes the LOCK Device Dependent
Command. The XUNLOCK routine executes the UNLOCK Device
Dependent Command.

Address — $C7C

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

CHAPTER SEVEN

Functions:

1) The XLOCK entry sets the LOCK bit value, DFDLOC ($20),
into TEMP4. The XUNLOCK entry sets a zero value into TEMP4.
Both routines then go to XLCOM.

2) The filename is decoded via the FNIDCODE routine.

3) The directory is searched for the first file entry match. If no
match is found, the ERFNF (file not found) exit is taken.

4) The files directory flag is modified to either LCX3KED or
UNLCXZlKED by means of the value previously set into TEMP4.

5) The Directory sector is written back to the disk.

6) The CSFDIR routine is called to find the next filename match.
If a match is found, then the process repeats at step four. If no
match is found, then exit via FGREAT.

XPOINT

Th(; XPOINT routine executes the POINT Device Dependent
Command.

Address - $CBA

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) If the FCBFLG indicates that the file can acquire sectors
(Opened for Output or Append), then exit via the ERRPOT
(point error) exit.

2) If the current sector is not the same as the sector POINTed to
by the lOCB AUX3 and AUX4 fields, then write the current
sector back to the disk (if it has been changed).

3) Read the POINTed to sector into the sector buffer.

4) Set the FCB next byte pointer, FCBDLN, to the value
indicated by the user Point data in the lOCB AUX5 field.

5) Exit to FGREAT.

XhlOTE

The XNOTE routine executes the NOTE Device Dependent
Command.

CHAPTER SEVEN

Address - $D03

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) The current sector number and data displacement into the
sector is moved to the appropriate ICXHB fields, ICAUX3,
ICAUX4, 1CAUX5.

2) Exit via GREAT.

Chapter Eight

FMS

OPEN

ROUTINES

The FMS Open routine, DFMOPN, is called directly by CIO via the
FMS Device Vector Table, DFMSDH at $7CB.

DFMOPN

The DFMOPN routine is the FMS file open routine.
Address - $8AB
Entry Registers — A = Don't Care.

X = lOCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) Initialize for this operation by calling SETUP.

2) Decode the filename via FNDCODE.

3) Examine the open code in ICAUXl for the open-for-directory-
read command. If this is a directory read command, go to
LISTDIR.

4) If not a directory read, then search the directory for the first
match on the file name and save the resulting search condition
on the stack.

5) Determine the exact type of Open operation to be performed
by examining the lOCB ACUXl field. If INPUT, go to DFOIN.
If Output, go to DFOUT. If Update, go to DFOUPD. If Append,
go to DFOAPN. If none of the above, exit via the ERDVDC
(device command error) exit.

CHAPTER EIGHT

DPOIN

DFOIN ($8D8) is entered when opening a file for Input. The routine
pops the stack to determine if the directory search for the file name
was successful. If the file name was found in the directory, then go to
DFOUI. If the search was not successful, then exit to ERFNF (file not
found).

DI^OUPD

DFOUPD ($8DD) is entered when opening a file for Update (Input
and Output). The routine pops the stack to determine if the file name
was found in the directory. If the file was not found, then exit to
ERFNF (file not found). If the file was found, insure that the file is
noi: Locked by calling TSTLOCK. If the file is unlocked, then continue
at 13FOUI.

DFOUI

DFOUI ($8E3) is entered to finish opening a file for Input or Update.
The read setup routine, DFRDSU, is called. FMS then exits via the
GREAT exit.

DFDRDSU

DFDRDSU ($9AE) is entered to set up a data file for reading. It
beg:ins by calling SETFCB to set some standard file information into
the FCB. It continues by setting up the FCB with various other
parameters to read the first data sector in the file. This sector is read
via the RDNSO routine. When the sector has been read into the
sector buffer, the code returns to the caller.

DFOAPN

DFOAPN ($BEC) is entered to open a file for Append.

1 ) Pop the stack to determine if the file has been found in the
directory. If the file was not found exit via ERFNF.

2) if the file was created by DOS 1 , then exit via ERAPO.

3) Insure the file is not locked by calling TSTLOCK.

4) Insure the diskette is not write protected by calling
OPVTOC.

5) Allocate a new sector for the start of the Append chain by
calling GETSECTOR.

6) Save the sector number of the sector obtained in FCBSSN so
that it will be available when the file is closed.

CHAPTER EIGHT

7) Continue opening the file as if it were being opened for
Output at DHFOX2.

DI=OOUT

The DFOOUT ($911) routine is entered when opening a file for
Output.

1 ) Pop the stack to determine if the file was found in the
directory.

2) If the file was found, then delete it via the XDELO ($C53)
routine.

3) If the file was not found, then make a new entry in the directory
via the code at DFOXl ($9 ID).

4) Allocate a data sector for the file via the GETSECTOR
routine.

5) Put the necessary information about the file into the directory
and write the directory sector back to the disk.

6) Continue at DHFOX2.

Dlf1FOX2

DHFOX2 ($97C) is entered to finish the Open process for files that
are being opened for Output or Append.

1) Finish initializing the FCB via SETFCB.

2) If the TSTEKDS routine determines that the file name being
opened is DOS. SYS, then write out DOS via the WRTDOS
routine.

3) Exit via GREAT.

SIITFCB

The SETFCB ($995) routine is used in the various Open file routines
to place certain common data into the FCB.

Chapter Nine

FMS

ROUTINES

The; FMS close routine is called directly by CIO via the FMS Device
Vector Table, DFMSDH at $7CB.

DFMCLS

Address -$B15

Entry Registers - A = Don't Care.

X = lOCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1) Initialize via call to SETUP.

2) If the file was not opened for some form of output (Output,
Update or Append) then clear the FCB open flag, FCBOTC and
exit via FGREAT.

3) If the FCBFLG indicates that the file has not acquired sectors,
then continue at CLUPDT to close the Update file.

4) Write the last data sector via WRTLSEC.

5) Read the file's directory sector into the directory buffer via the
RRDIR routine.

6) Get the sector count from the directory.

7) If the file was opened for Output (i.e. it is not open for
Append), then continue at CLOUT.

8) Read all the data sector of the file until the end-of-file sector
is found.

9) Place the sector address of the start of the Append chain into
the link sector field of the (old) end-of-file sector.

10) Continue at CLOUT.

CHAPTER NINE

CLOUT

The CLOUT ($B50) routine is entered to finish closing a file that had
been opened for Output or Append.

1 ) The sector count field of the directory is updated.

2) The open for output flag is turned off.

3) The file in use flag is set.

4) The directory sector is written back to the disk by the DRTDIR
routine.

5) The VTOC sector is written back to the disk by the
WRTVTOC routine.

6) The FCB open code flag, FCBOTC, is cleared to zero.

7) Exit via FGREAT.

CLUPDT

The CLUPDT ($B75) is called to finish the closing of a file that had
been opened for Update.

1 ) If the current sector in the sector buffer has been modified
then write it back to the disk via the WRCSIO routine.

2) Clear the FCB open flag, FCBOTC, to zero.

3) Exit via FGREAT.

Chapter Ten

GET BYTE
ROUTINE

The FMS GET BYTE routine, DFMGET, is called directly by CIO
via tlie FMS Device Vector Table, DFMSDH at $7CB. The GET
BYTE routine's function is to get and return the next sequential data
byte to CIO.

DFMGET

Address - $ABF

Entry Registers - A = Don't Care.

Y = lOCB number times 16.
X = Don't Care.

Exit Registers - A = Unknown.

Y = Unknown.
X = Unknown.

Functions:

1 ) Initialize via the SETUP routine.

2) If the FCB is opened for Directory read, then go to
GDCHAR.

3) If the current sector is empty, attempt burst I/O (see Burst I/O
section), then continue with number four.

4) Read the next sector via the RDNXTS routine. If the read
sector operation did not return an end-of-file condition, then
continue at step three, else exit via ERREOF (end-of-file error).

5) Get the data byte from the sector and place it in SVDBYT for
the exit routines.

6) If the next byte in the file is the end-of-file byte, exit via
RETURN with the impending end-of-file condition code ($03),
else exit via GREAT.

Chapter Eleven

PUT BYTE
ROUTINE

The FMS PUT BYTE routine, DFMPUT, is called directly by CIO
vin the FMS Device Vector Table, DFMSDH at $7CB. The PUT
B^fTE routine's function is to place the single data byte transmitted by
CIO into the data sector.

DIFMPUT

Address -$99C

Entry Registers - A = The "put data" data byte.

X = The lOCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1 ) The data byte in the A register is saved in SVDBYT.

2) SETUP is called to initialize for this operation.

3) If the caller was not CIO, then prevent a burst I/O operation
from occurring.

4) If the file was not opened for output, then exit via ERDVDC
(device command error).

5) If the current data sector is full, write the sector via WRTNXS,
then attempt burst I/O (see BURST I/O section). If a burst I/O
operation did take place, then get the next byte after the area
just written by burst I/O and place it into the SVDBYT cell.

6) Increment the sector data byte count.

7) Move the data byte from SVDBYT to the next available data
byte in the sector.

8) Set the sector modified flag in the FCB.

9) Exit via GREAT.

Chapter Twelve

BURST I/O

The CIO is designed to fill or empty a large user buffer with data bytes
sent to or received from a device handler, a byte at a time. To fill a
thousand-byte buffer, CIO would have to call FMS one thousand
times in rapid succession. While the process is simple and easy to
implement by both CIO and the Device Handlers, it can be very
slow. This is particularly true in the case of FMS which has a great
deal of overhead code to go through each time it is called. FMS
circLimvents most of the CIO/FMS calls for large data transfers via the
BURST I/O routines.

Burst I/O operates by reading or writing data sectors directly into
the user buffer (Figure 1, data path I). There are a number of tests
that must be passed before a burst I/O operation can take place. If any
of the tests fail, then the CIO/FMS data transfer reverts to the normal
mode of operation.

When the PUT BYTE routine is called, it will call the WTBUR
($A1F) routine when it is ready to start filling a new data sector.
WTBUR will not allow a burst I/O operation to happen if the file has
been opened for Update. If the file has not been opened for Update,
then WTBUR goes to the common read/write burst I/O test routine,
TBL'RST at $A28. If the file has been opened for Update, then exit
Burst I/O indicating that a Burst I/O did not happen. When WTBUR
calls TBURST, it has the A register set to non-zero to indicate that it
is write.

When the GET BYTE routine is called, it will call the RTBUR
($A26) routine when it is ready to read a new data sector. RTBUR
indicates that it is read by setting the A register to zero and then
enters TBURST.

TBURST

1 ) Save the A register in BURTYP. This value will indicate if
the burst operation is a read or a write.

2) If the I/O command in the lOCB is for text I/O (a transfer
that is to end when the Atari end-of-line ($9B) character is
transferred), then TBURST will exit indicating (carry set) that a
burst I/O operation did not occur.

CHAPTER TWELVE

3) If the user buffer length in the lOCB is not at least a full
sector in size, then exit without doing a burst I/O.

4) If all the above tests pass, then perform a burst I/O operation.
The first step in the burst I/O operation is to change the zero
page sector buffer pointer, ZXBA ($47) from the FMS sector
buffer address to the user buffer address.

5) If the operation is read, then read the next sector via RDNXTS.
If the read sector operation produced an end-of-file, then go to
BUREOF, else go to BBINC.

6) If the operation is write, then the area in the user buffer,
where the three bytes of data sector control information is to be
placed, will be saved. The data will be written via the WRTNXS
routine. The saved user data will then be copied back into the
user buffer. The code then continues at BBINC.

BBINC

The BBINC routine is entered after a single burst I/O sector has been
read or written. BBINC updates data counters in the FCB and in the
\OCB and tests for the end of the Burst I/O.

1 ) The zero page sector buffer pointer is incremented by the
length of data in a sector (125 or 253).

2) The user buffer length is decremented by the length of data in
a sector.

3) The TBLEN routine is called to determine if there is enough
room left in the user buffer to read or write another full sector

( 128 or 256 bytes). If another sector can be read or written, then
the process repeats at NXTBUR ($A3E).

4) If there is not enough room in the user buffer to perform
another full sector read or write, then BUREOF is entered.

BUREOF

1) The final address in the zero page sector pointer, ZSBA ($47),
is moved to the lOCB buffer address field.

2) The value in the zero page sector buffer pointer is restored by
the SSBA routine.

3) The caller is returned to with the carry cleared to indicate
that a burst I/O operation has happened.

Chapter Thirteen

READING

THE DIRECTORY

AS A FILE

A formatted subset of the data in the Directory can be read as if the
Direi:tory were a disk file. This is accomphshed by using the open
directory code ($02) in the lOCB ICAUXl byte. When FMS
recognizes this code in the Open routine (at $8B1), it will go directly
to the LISTDIR routine. The LISTDIR routine prepares the FCB for
reading the directory as a file. The GET BYTE routine will recognize
the read directory condition from information stored in the FCBOTC
field (see $AC2) and go directly to the directory read character I/O
routine GDCHAR.

LISTDIR

Address - $DAD

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = Unknown.

Y = Unknown.

Functions:

1) The TEMP4 byte is used to count the characters that have
been transmitted by GDBYTE from the formatted line buffer.
LISTDIR sets this value to zero to indicate the start of a new
formatted line.

2) The SFDIR routine is called to start a wild card search for the
file name in the directory.

3) If a match is found then FDENT is called to format the entry
and prepare for the GDBYTE calls. Exit via GREAT.

4) If a match is not found, then LDCNT is called to prepare to
send the xxx FREE SECTORS line.

CHAPTER THIRTEEN

GDCHAR

G1X:HAR ($DB9) is entered from GET BYTE to get a single data
byte from a formatted directory line.

1) The TEMP4 flag is tested. If the value is negative, then all
formatted information has been transmitted. Exit is via the
ERREOF (end-of-file error) exit.

2) The value in TEMP4 is used as an index into the formatted
line buffer to get the next character. The character is placed into
SVDBYT for loading into the A register by the RETURN
routine.

3) The character retrieved from the buffer is examined for the
EOL ($9B) character.

4) If the character is not an EOL, then exit is via GREAT.

5) If the character was an EOL, then the line length is examined
to see if the line was a directory entry line (i.e. , if the length was
17) or the final xxx FREE SECTORS.

6) If the line was the final line, then TEMP4 is set to a negative
value ($80) to indicate that all formatted lines have been sent.
Exit is via GREAT.

7) If the line was not the final line, then CSFDIR is called to
find the next matching file name.

8) If a file name match is found, then FDENT is called to format
the found entry into the formatted line buffer. Exit is via
GREAT.

9) If a file name match is not found, then go to LEXI^NT to
format the final line.

LDCNT

LIX^NT ($DE9) formats the final line of a directory read.

1) Read the VTOC.

2) Get the free sector count from the VTOC and convert it to
ATASCII via the CVDX routine.

3) Move the FREE SECTORS message to the formatted line buffer.

4) EXIT is via FGREAT.

FDENT

The FDENT ($E21) routine formats the current directory entry into
the formatted line buffer for subsequent reading by GDBYTE.

1) The directory flag is checked for the file locked condition. If

the file is locked, then the "*" is placed in the formatted line.

2) The file name is moved from the directory entry to the
formatted line.

3) The file sector count is converted to AT ASCII and placed in
the formatted line.

4) The EOL character is placed in the formatted line.

5) Exit is via the RTS instruction.

Chapter Fourteen

SECTOR

I/O
ROUTINES

The FMS performs sector I/O by calling the SIO routine in the OS
ROM (Figure 1, control path 3). All sector I/O calls in the FMS occur
frorri the BSIO routine. There are several other routines that are
designed to set up information for BSIO. These routines deal with
reading and writing sectors of a particular type such as data sectors,
directory sectors, and the VTOC sector.

BSIO

Address — $76C

Entry Registers - A = Sector number most significant byte.

Y = Sector number least significant byte.
X = If 1, then 128 byte I/O (810 drive).

If 2, then 256 byte I/O (815 drive).
Exit Registers - A = Status byte from DCB.

Y = Unknown.

X = lOCB and FCB number times 16.

CHAPTER FOURTEEN

Functions:

1) The sector number is stored in the DCB from the A,Y register
pair. The EXHB is the interface control block for SIO calls.

2) If the carry is clear, then the DCB is set up for read data. If
the carry is set, then the DCB is set up for write data.

3) The serial bus ID for the disk, and the disk timeout values are
placed into the DCB.

4) The error retry counter, RETRY, is set for four retries.

5) The I/O data length is set to 128 or 256 depending upon the
data in the X register.

6) The serial I/O routine ($E459) is called to execute the I/O.

7) If the I/O operation was good, then the X register is loaded
with the lOCB (and FOB) number times 16 from the CRFCB
cell and the status byte from the DCB is loaded into the A register.
Return is via the RTS instruction.

8) If the I/O operation was bad, then the retry counter is
decremented. If the retry value is positive, then the I/O is retried.
If the value is negative, then the routine is exited in the manner
described in step seven.

Ds;io

The DSIO routine is called to perform data sector I/O operations.
Address -$11F7
Entry Registers - A = Sector number most significant byte.

Y = Sector number least significant byte.
X = lOCB and FCB number times 16.

Exit Registers — A= I/O condition code.

Y = Unknown.

X = lOCB and FCB number times 16.

Functions:

1 ) The sector buffer address is obtained from the zero page sector
buffer pointer ZSBA ($47) and placed in the DCB buffer address
field, DCBBUF.

2) The drive type byte is loaded into the X register from DRVTYP.
If the drive is an 810, then the value will be one. If the drive is
an 815, then the value will be two.

3) BSIO is called.

4) The DSIO caller is returned to via the RTS instruction.

CHAPTER FOURTEEN

RDDIRAndWRTDIR

The RDDIR and the WRTDIR routines are used to perform Directory
sector I/O operations. The RDDIR entry ($106E) sets the carry to
indicate read. The WRTDIR entry ($1071) clears the carry to indicate
write. Both of the routines continue at DIRIO.

DIRIO

1) Save the read/write flag (carry sense) on the stack.

2) Set the address of the directory buffer into the DCB buffer
field, DCBBUF.

3) The CDIRS cell contains the number of the directory sector
to be read or written. This value ranges from zero to seven. The
DIRIO routine creates the actual sector number to read or write
by adding $169 to the CDIRS value. The resulting sector number
is placed in the A, Y register combination.

4) Continue at DSYSIO.

RDWOC And WRTVTOC

The RDVTOC and WRTVTOC routine are called to initiate I/O to
and from the VTOC sector. The RDVTOC routine ($108B) first
checks the write required byte in the VTOC sector buffer. If the value
of this byte is not zero, then the VTOC is already in the buffer (and
has been changed). If the VTOC is already in the buffer, then the
read does not have to be done; therefore, the RDVTOC routine will
return to the caller. If the write-required byte is zero, then RDVTOC
will clear the carry to indicate that the operation is read. The
WRTVTOC routine ($1095) sets the write required byte to zero, then
sets i:he carry to indicate a write operation. Both Rt)VTOC and
WRTVTOC continue at VTIO.

VTIO

1 ) The read/write flag is pushed onto the stack.

2) The VTOC sector buffer address is moved from the zero page
drive buffer address pointer ZDRVA ($45) to the DCB buffer
pointer, DCBBUF.

3) The A,Y register combination is loaded with the VTOC
sector number ($168).

4) Continue at DSYSIO.

DSYSIO

1 ) The read/write sense is popped from the stack.

CHAPTER FOURTEEN

2) The drive type value is loaded into the X register from
DRVTYP.

3) BSIO is called.

4) If the I/O operation was good, then return to the caller via the
RTS instruction.

5) If the I/O operation was bad, the exit via the ERRSYS exit
(fatal system I/O error).

OI>VTOC

The OPVTOC routine ($10BF) is used by various FMS routines to
insure that the diskette is not write protected before executing functions
that will write to the disk. This routine will read the VTOC via
RDVTOC and then attempt to write the VTOC via WRTVTOC. If
the diskette is write protected, the WRTVTOC will cause an I/O
error exit (error number 144). If the diskette is not write protected,
then the routine will return to the caller. When OPVTOC does
return to the caller, the current disk VTOC is in the drive buffer.

Chapter Fifteen

FILE NAME
DECODE
ROUTINE

The FNEXI^ODE routine is used to transform the user suppUed file
name into a form that is usable in FMS for wild card searching of the
direc:tory. The primary and extension parts of the user file name are
padded with blanks and question marks as required. The following
examples show the types of transform performed by FNEXDODE:

User File Name

Transformed File Name

D:*.*

77777777777

Dl:GLOP.*

GLOP ???

Dl:GLOP.BAS

GLOP BAS

D2:*.ASM

????????ASM

D:GL?P.S*

GL?P S??

D1:G*

G7777777

FNC»CODE

Address - $E9E

Entry Registers -

-A

= Don't Care.

= lOCB and FCB number times 16.

= Don't Care.

Exit Registers —

= Unknown.

= lOCB and FCB number times 16.

= Unknown.

Functions:

1 ) The user file name buffer is searched for the colon (:) delimiter.
If the delimiter is not found within 256 characters then exit to
ERRFN routine (file name error).

2) The FMS file name buffer, FNAME, is cleared to blanks.

3) The EXTSW byte is set to zero. When EXTSW is zero, the
primary file name field is being processed. When EXTSW is

CHAPTER FIFTEEN

minus, then the extension file name field is being processed.

4) The next character in the user file name buffer is examined.

5) If the character is an asterisk ('), then the field is padded with
question mark characters to the end of the field.

6) If the character is a period and the extension field is being
processed, then exit via the RTS instruction.

7) If the character is a period and the primary field is being
processed, then switch to the extension field processing.

8) If the character is a question mark, then put it into the FN AME
via FDSCHAR.

9) If the character is alphanumeric (A through Z, or through
9), then put it into FN AME via FDSCHAR.

10) If the character is none of the above, then assume that end
of the filename has been found and exit via the RTS instruction.

11) If a character was stored, then continue at step four.

FDSCHAR

1 ) If the character counter register, X, indicates that the primary
field is full, then exit without storing the character.

2) If the character counter register, X, indicates that the extension
field name is full, then exit without storing the character.

3) Store the character into FN AME indexed by the X register.

4) Increment the X register.

5) Return to caller via the RTS instruction.

Chapter Sixteen

DIRECTORY
SEARCHING

The Directory search routine searches the directory entries for a file
name that matches the name in FNAME. The routine has two entry
points: SFDIR which is used to begin the search at the start of the
directory, and CSFDIR, which is used to continue searching the
directory at the entry just past the previously found matching entry.

The routines have five memory cells that they use for controlling
the search operation: DHOLES, DHOLED, CDIRS, CDIRD and
SFNUM. The CDIRS cell contains the current relative directory
sector number (zero through seven). The CDIRD cell contains the
displ acement into the directory sector of the current entry. DHOLES
gives the relative directory sector number (zero through seven) of the
first hole or available entry in the directory. TTie DHOLED cell gives
the displacement to the first available entry that is the hole. The
SFNUM cell is used to contain the current file number of the entry
being examined. The value in SFNUM will be from zero through 63.

If the value of DHOLES is $FF at the end of the search, then the
directory is full.

The directory search routine will exit with the carry clear if a
match was found. It will exit with the carry set if no matching entry
was found.

SFDIR

The SFDIR routine ($F21) is called to start searching the directory at
the start of the directory.

1) Initialize DHOLES, CDIRS, SFNUM to $FF.

2) Initialize CDIRD to $70.

3) Continue at CSFDIR.

CSFDIR

The CSFDIR routine ($F3 1 ) is called to continue searching the
directory.

1) Increment the file number, SFNUM.
48

CHAPTER SIXTEEN

2) Increment CDIRD by the size of a directory entry (16).

3) If the CDIRD is now greater than, or equal to, 128 ($80) then
increment CDIRS by one. If the value of CDIRD is now eight,
then exit with the carry set to indicate that a match was not
found. If CDIRD is less than eight, then read the next directory
sector via RDDIR. Set CDIRD to zero.

4) If the directory entry flag field is zero then the end of the used
portion of the directory has been reached. If a hole has not been
found, then mark this entry as a hole. Exit with the carry set to
indicate that the file was not found.

5) If the directory entry flag field indicates that the file is open
for output, then skip this entry.

6) If the directory entry flag field indicates that the file has been
deleted, and a hole has not been found, then mark this entry as a
hole and continue searching the directory.

7) If the file is in use, then check the file name in the directory
entry for a match with the name in FNAME. Wild card characters
in FNAME (question marks) are assumed to match the
corresponding characters in the directory entry file name.

8) If the names match, then exit with the carry clear to indicate
that a match was found.

9) If a match was not found, then continue to search the
directory.

Chapter Seventeen

WRITE

SECTOR

The write next sector routine, WRTNXS, is used to write a data
sector to disk.

Address - $F94

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers — A = Unknown.

X = lOCB and FCB number times 16.

Y = Unknown.

Functions:

1 ) If the file has been opened for update, and the sector has not
been modified, then do not write the sector. Read the next data
sector and then return to caller.

2) If the file has been opened for update, and the sector has been
modified, then write the current sector. Read the next data
sector into the sector buffer and return to the caller.

3) If the file is not opened for update, then allocate a new sector
to the file by calling GETSECTOR.

4) Move the sector byte count from the FCB FCBDLN field to
the data sector byte count field.

5) Move the address of the newly acquired sector from the FCB
FCBLSN field into the link field of the current data sector.

6) Write the current sector to the disk via WRCSIO.

7) If the I/O was bad, mark the FCB by placing a zero value into
FCBOTC as closed and exit via RETURN with the I/O error
number as the return code.

8) If the I/O was good, then increment the FCB sector counter
field, FCBCNT.

9) Call MVLSN to move the sector number of the link sector
number field of the FCB, FCBLSN, to the current sector number
field of the FCB,FCBCSN.

10) Set the current data length field of the FCB, FCBDLN, to
zero.

11) Set the maximum data length field of the FCB, FCBMLN,
to 125 (if 810 drive) or 253 (if 815 drive).

12) Return to user via the RTS instruction.

Chapter Ei

READ

SECTOR

Th«; read next sector routine, RDNXTS, reads the next sector in the
file sector chain into the sector buffer. If there are no more sectors in
the chain, then the routine returns with the carry set to indicate end-
of-file. If the routine returns with the carry clear, then the next sector
has been read.

RDNXrS

Address -$100F

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = lOCB and FCB number times 16.

Y = Unknown.

Functions:

1) If the file has been opened for Update, then WRTNXS is

CIHAPTER EIGHTEEN

called to write the current sector if it has been modified.

2) If the FCB link sector number field, FBCLSN, is zero then
there are no further sectors to read. Return to the caller with the
carry set to indicate that the end-of-file has been reached.

3) Call MVLSN to move the FCB link sector number field,
FCBLSN, the FCB current sector number field, FCBCSN.

4) Call RWCSIO with the carry set to read the next sector.

5) If the I/O operation was bad, exit via the ERRIO exit (I/O
error) .

6) Insure that the file number in the sector just read agrees with
the file number in the FCB. If the file numbers are not the same,
exit via the ERFNMM exit (file number mismatch). Note: if the
routine was called by delete, return to delete indicating end-of-
file.

7) Move the link sector number from the data sector to the FCB
link sector field in the FCB, FCBLSN.

8) Move the sector data length information from the data sector
to the FCB maximum data length field, FCBMLN.

9) Reset the FCB data length field, FDBDLN, to zero.

10) Return to the caller with the carry clear to indicate that a
sector has been read.

Chapter Nineteen

GET AND

FREE

SECTOR

ROUTINES

TbiC get sector routine, GETSECTOR, is called when a new sector is
needed. The routine searches the bit map in the VTOC for a free
sector. The sector found is deallocated from the bit map and the
sector number is returned to the caller. The free sector routine,
FR.ESECT, is given a sector number to be freed. FRESECT locates
the required bit map bit in the VTOC and turns it on (sets it to one).
The sector is now eligible for reuse.

GETSECTOR

Address -$1106

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.

Exit Registers - A = Unknown.

X = ICXIlB and FCB number times 16.

Y = Unknown.

Functions:

1 ) The Y register is used as an index into the bit map bytes.

2) The bit bytes are examined sequentially from the first bit map
byte to the last bit map byte until a non-zero byte is found. The
displacement to this byte is saved in TEMPI.

3) If no bits are found in the bit map, then the ERRNSA exit
(no sectors available) is taken.

4) The number-of-sectors-available-field, in the VTOC, is
decremented by one.

5) The VTOC write required byte in the VTOC is set to a non-

CHAPTER NINETEEN

zero value to indicate that the VTOC has been changed and
must be written back to the disk.

6) The non-zero bit map byte that was found in the bit map
search is retrieved. The bits in this byte are shifted left until a bit
moves into the carry flag. The carry is then set clear and the bits
shifted back to their original position. The byte with the newly
allocated sector bit turned off is placed back into the bit map.

7) The number of bits shifted and the index to the bit map byte
are used to develop the sector number represented by the Ijit.

8) The sector number is stored in the FCB link sector field,
FCBLSN.

9) The user then returned to via the RTS instruction.

FRIESECT

Address -$10C5

Entry Registers - A = Don't Care.

X = lOCB and FCB number times 16.

Y = Don't Care.
Exit Registers - A = Unknown.

X = lOCB and FCB number times 16.

Y = Unknown.

Furictions:

1 ) The sector to be freed is in the FCB current sector field,
FCBCSN. If the sector number is zero, then FRESECT exits
back to the user via the RTS instruction.

2) The sector number is divided by eight to determine the bit
map byte which represents the sector. The remainder from this
division represents the bit within the byte.

3) The byte is retrieved from the bit map, the bit is turned on,
and the byte placed back into the bit map.

4) The number of available sectors field in the VTOC is
incremented by one.

5) The VTOC write required byte is set to non-zero to indicate
that the VTOC has been changed and needs to be written back
to the disk.

6) The caller is returned to via the RTS instruction.

Chapter Twenty

THE
BOOT PROCESS

When the Atari computer is turned on, the routines in the OS ROM
will (under certain conditions) read the first sector from the disk in
drive one into memory. It will then examine certain specific locations
in this record to decide how to boot the disk. In the following
discussion, refer to Figure 20-1. The OS ROM code will load BRCNT
consecutive sectors (starting with sector one) onto memory, starting
at the address contained in BLDADR. When the OS ROM code has
finished this task, it will make a JSR call to the code that is seven
bytes into the start of the boot area. In the case of FMS, this is the
JMP XBCONT instmction at $706. The XBCONT code will continue
the boot load process.

The XBCONT code examines the DFSFLG to see if a DOS. SYS
file exists. If the file exists, then the sector number of the first sector
in DOS. SYS will be in DFLINK. The routine will then read all the
sectors in the chain starting at DFLINK into the memory area pointed
to by DFLADR. When the entire DOS. SYS file is read into memory,
X13CONT returns to the OS ROM code.

The OS ROM code will eventually vector through the BINTADR
so that the FMS can initialize itself. In the DOS 2. OS system,
BINTADR points into the DUP.SYS code. DUP.SYS then receives
control from the OS ROM rather than the FMS. One of the tasks that
DUP.SYS performs during its initialization is to call the FMS
initialization routine.

XBCONT

The XBCONT routine ($714) is entered by the OS ROM code during
tbie boot process to allow the boot process to continue in the manner
best suited for the code being booted.

Functions:

1) If the DFSFLG indicates that a DOS. SYS file does not exist,
then the OS ROM is returned to with the carry set to indicate
that the boot has failed.

CHAPTER TWENTY

2) The address contained in DFLADR is moved to the zero page
address pointer, ZBUFP, and to the DCB buffer pointer field,
DCBBUF.

3) The sector number contained in DFLINK is loaded into the
A, Y register pair, the carry is cleared to indicate read, and BSIO
is called to read a DOS. SYS sector.

4) The next sector link is obtained from the link field of the data
sector just read.

5) If the sector link value is zero, then the DOS. SYS end-of-file
has been reached. The OS ROM will be returned to with the
carry clear to indicate that the boot read was good.

6) If the sector link value is not zero, then the zero page buffer
pointer and the EXHB buffer pointer are incremented by the
amount of data in the sector (125 for 810 drives, 253 for 815
drives).

7) The process continues by reading the next sector into
memory.

Sector 1

Sector 2

$700

$780

Sector 3 $800

$700

BFLAG

Flag( = 0)

$701

BRCNT

Number of Consecutive Sectors to Read

$702

BLDADR

Address to Load Boot Sectors at

$704

BIWTARR

Initialization Address

$706

JMPXBCONT

Boot Continue Vector

$709

SABYTE

Number of Sector Buffers to Allocate

$70A

DRVBYT

Drive Bits

$70B

Unused

$70C

SASA

Buffer Start Address

$70E

DFSFLG

DOS Flag

$70F

DFLINK

Sector Pointerto DOS.SYS File

$711

BLDISP

Displacement in Sector to Sector Link

$712

DFLADR

Address of Start of DOS.SYS File
Figure 20-1

Boot Records

Chapter Twenty-One

MAINTAINING

THE
BOOT RECORD

The boot record (sector 1) contains information about the DOS. SYS
file. When LX)S.SYS is opened for output, FMS will write all of FMS
out to the disk as part of the open process. It will also modify sector
zero to indicate that a CXDS.SYS file exists and to indicate where on
the disk it is. If DOS. SYS is ever Deleted or Renamed (to something
not DOS. SYS), then the boot record must be modified to indicate
that a DOS. SYS file does not exist. If a file is ever renamed to
EX)S.SYS, then the boot record is modified to point to the new
DOS. SYS file.

WRTDOS

The WRTDOS routine ($120A) is used to write a new DOS. SYS file
to disk and to update the boot record to indicate that a EXDS.SYS file
exists.

Functions:

1 ) The sector number which is contained in the FCB sector
number link field, FCBLSN, is used as the first sector of the
DOS. SYS file. This sector number is placed in the boot record
area in page seven along with the other necessary information.

2) Sectors one, two, and three are written from the memory area
from $700 through $87F.

3) The FMS is written to the EXDS.SYS via the WDO routine.

4) Exit is via GREAT.

WDO

Tl-ie WDO routine ($1267) is used to write the FMS to the DOS.SYS
file.

Functions:

1 ) The address contained in DFLADR is moved to the zero page

CMAPTER TWENTY-ONE

buffer pointer, ZBUFP.

2) The FMS is copied from its area in memory to the file sector
buffer in 125 byte chunks.

3) The buffers are written to disk by the WRTNXS routine.

4) The process continues until the entire FMS area has been
written.

5) The caller is returned to via the RTS instruction.

DliLDOS

Tbe DELIX)S routine ($1219) is used to modify the boot record to
indicate that DOS. SYS does not exist.

Functions:

1) The DFSFLG is set to zero to indicate that DOS. SYS does not
exist.

2) The area from $700 to $87F is written to sectors one, two,
and three.

3) The caller is returned to via the RTS instruction.

ATARI
DOS
2.0S

Thii listing is protected against unauthorized reproduction by the Copyright Law of the United
Stales. Any reproduction utiUzed for profit or other commercial advantage is precluded without
the specific prior written authorization of Optimized Systems Software, Inc., the owner of the
cop /right. Any such reproduction does not constitute fair use and may subject the individual to
both civil and criminal penalties. Federal Law provides for a maximum fine of $10,000 or
imprisonment for not more than one year, or both, for infringement of this copyright.

Contact the President, Optimized Systems Software, Inc., 10379 Lansdale Avenue, Cupertino,
California, 95014, prior to reproducing or utilizing any portion of this listing. Any attempt to
change the form of publication of this listing, that is, rendering it into machine-readable form or
othjrwise, is a precluded reproduction if done for profit or other financial advantage.

ATARI DOS 2.0S

FMS - 128/256 BYTE SECTOR {2.0S)

0030

1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026

1027
1028 ;

System Equates

.PAGE " Copyright and Author Notice —

THIS PROGRAM MAY NOT BE REPRODUCED,
STORED IN A RETRIEVAL SYSTEM, OR
TRANSMITTED IN WHOLE OR IN PART,
IN ANY FORM, OR BY ANY MEANS, BE IT
ELECTRONIC , MECHANICAL, PHOTOCOPYING,
RECORDING, OR OTHERWISE WITHOUT THE
PRIOR WRITTEN PERMISSION OF

OPTIMIZED SYSTEMS SOFTWARE, INC.

10379 LANSDALE AVENUE

CUPERTINO, CALIFORNIA 95014 (U.S.

A.)

PHONE: (408) 446-3099

***********************************

PROGRAMMER PAUL LAUGHTON
UPDATED: 19-AUG-80

.***********************************

0000

0700
0043
03 40
0003
03 00
E453
00 9B
03 lA
0020
02E7
1540
0102
00 DF

0246

000F

1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044

.PAGE " System Equates"
***********************************

FMSORG =
FMSZPG =
lOCBORG =
LMASK =
DCBORG =
DHADR =
EOL

DEVTAB =
ZICB

LMADR =
DUPINIT =

1045 STAR

1046 OSBTM =

1047 DSKTIM

1048 TIMOUT =

$700

?43

$340

$300

$E453

$9B

$31A

$20

$2E7

$1540

$102

$DF

$246

;LINK MASK

rlNIT ADDR FOR DUP

; STACK LOC FOR PUT BYTE

;HI BYTE OF ADDR LESS THAN OS

SPACE
rADDR OF OS WORST CASE DISK

TIME OUT
;TIME OUT VALUEE OF 15 SECS.

0000

1049

0000

1050

1051

1052

1053

1054

1055

1056

.PAGE " lOCB"
*= lOCBORG

lOCB - 10 CONTROL BLOCK
THERE ARE 8 1/0 CONTROL BLOCKS
1 lOCB IS REQUIRED FOR EACH
CURRENTLY OPEN DEVICE OR FILE

ATARI DOS 2.0S

034»
0341
034:2
0343
0344
0343
034'5
03413
0349
034A
034:3
03 40
0340
034E
034F
0010

0350

0001
0002
0003
0004
0005
0006
000 7
0008
00e9
00eA

00eB
00ec
00eD

00i'E
00CIE
00C1F

0001
00(12

1057 lOCB

1058 ICHID

*—

*+l ;

DEVICE NUMBER

1059 ICDNO

*—

*+l

DEVICE HANDLER

1060 ICCOM

*—

*+l

I/O COMMAND

1061 ICSTA

*+l ;

I/O STATUS

1062 ICBAL

*+l

1063 ICBAH

* —

*+l ;

BUFFER ADR (H,L)

1064 ICPUT

*—

*+2

PUT CHAR DH ADDR

1065 ICBLL

*—

*+l

1066 ICBLH

*ss

*+l

BUFFER LEN (H,L)

1067 ICAUXl

*+l ;

AUX 1

1068 ICAUX2

* —

*+l

AUX 2

1069 ICAUX3

*—

*+l

AUX 3

1070 ICAUX4

*—

*+l

AUX 4

1071 ICAUX5

*—

*+l

AUX 5

1072 ICAUX6

*—

*+l

AUX 6

1073 ICLEN

*-IOCB

1074 ;

1075

*+ICLEN*7

SPACE FOR 7 MORE lOCB'S

1076 ;

1077 ; ICCOM VALUE EQUATES

1078 ;

1079 ICOIN

$01

•OPEN INPUT

1080 ICOOUT

$02

fOPEN OUTPUT

1081 ICIO

$03

;OPEN UN/OUT

1082 ICGBR

$04

;GET BINARY RECORD

1083 ICGTR

$05

; GET TEXT RECORD

1084 ICGBC

$06

;GET BINARY CHAR

1085 ICGTC

$07

;GET TEXT CHAR

1086 ICPBR

$08

;GET BINARY RECORD

1087 ICPTR

$09

;PUT TEXT RECORD

1088 ICPBC

$0A

;PUT BINARY CHAR

1089 ICPTC

$0B

;PUT TEXT CHAR

1090 ICCLOSE =

$0C

;CLOSE FILE

1091 ICSTAT

$0D

;GET STATUS

1092 ICDDC

$0E

; DEVICE DEPENDENT

1093 ICMAX

$0E

;MAX VALUE

1094 ICFREE

$0F

;IOCB FREE INDICATOR

1095 ;

1096 ; ICSTA VALUE EQUATES

1097 ;

1098 ICSOK

$01

; STATUS GOOD, NO ERRORS

1099 ICSTR

$02

;TRUNCAIATED RECORD

lOCB

00193

1100

ICSEOF

$03

;END OJ

FILE

0080

1101

ICSBRK

$80

; BREAK

KEY ABORT

00131

1102

ICSDNR

$81

; DEVICE NOT READY

0032

1103

ICSNED

$82

;NON EXISTENT DEVICE

0033

1104

ICSDER

$83

;DATA ERROR

0034

1105

ICSIVC

$84

; INVALID COMMAND

0035

1106

ICSNOP

$85

; DEVICE/FILE NOT OPEN

0036

1107

ICSIVN

$86

; INVALID lOCB #

00 87

1108
1109

ICSWPC

$87

;WRITE

PROTECT

1110

r ZERO

PAGE

lOCB LABELS

1111

;

0021

1112

ICDNOZ

ICDNO-

-lOCB+ZICB

0028

1113

ICBLLZ

ICBLL-

■lOCB+ZICB

BUF LEN

0029

1114

ICBLHZ

ICBLH-

-lOCB+ZICB

0024

1115

ICBALZ

ICBAL-

-lOCB+ZICB

BUF ADDR

0025

1116

ICBAHZ

ICBAH-

-lOCB+ZICB

0022

1117

ICCOMZ

ICCOM-

-lOCB+ZICB

0026

1118

ICPUTZ

ICPUT

-lOCB+ZICB

•PUT RTN ADDR

ATARI DOS 2.0S

DCB

17A0
17A0

0300
0301
030 2
030 3
0304
0306
0303
030A

005:2
0050
0053
002 L

000:.

008].

008:!

0083
0084
008 V

1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160

.PAGE " DCB"
*= DCBORG

DCB - DATA CONTROL BLOCK
THE DCB IS AN lOCB LIKE CONTROL
BLOCK USED TO INTERFACE THE DISK
FILE MANAGEMENT SYSTEM TO THE
DISK HANDLER

DCB

DCBSBI *=

DCBDRV *=

DCBCMD *=

DCBSTA *=

DCBBUF *=

DCBTO *=

DCBCNT *=

DCBSEC *=

*+l
*+l
*+l
*+l
*+2
*+2
»+2
*+2

; SERIAL BUS ID

;DISK DRIVE #

; COMMAND

,-I/0 STATUS

;l/0 BUFFER ADDR (H,L)

;TIME OUT CNT

;l/0 BYTE COUNT

;l/0 SECTOR NUMBER

DCBCMD VALUE EQUATES

DCBCRS =
DCBCWS =
DCBCST =
DCBCFD =

'R
'P
'S
• 1

;Read sector ($52)

;Put sector ($50)

;Status request ($53)

r FORMAT DISKETTE ($21)

*** SPECIAL NOTE:

DCBCWS may be changed to 'W ($57)
if desired to have disk perform
a verifying read after each write.
Disk write ( 'W) operations will take
longer, but will be more reliable.

DCBSTA VALUE EQUATES

DCBSOK = $01 rSTATUS NORMAL

DCBDNR = $81 ; DEVICE NOT READY

DCBCNR = $82 ; CONTROLLER NOT READY

DCBDER = $83 ;DATA ERROR

DCBIVC = $84 ; INVALID COMMAND

DCBWPR = $87 ; WRITE PROTECT

030c:
030c:

004;:

004!;

0047
0049

004;.
004;.

ZERO PAGE

1161

1162

1163

1164

1165

1166

1167

1168

1169

.PAGE " ZERO PAGE"
*= FMSZPG

ZBUFP *= *+2

ZDRVA *= *+2

ZSBA *= *+2

ERRNO *= *+l

.•BUFFER PTR
;ZERO PG DRIVE PTR
;ZERO PG SECTOR BUF PTR
TERROR NUMBER

.INCLUDE #E:

.INCLUDE *D:ATFMS1.SRC

BOOT RECORD

004;>
004;,

2000
2001
2002
2003
2004

.PAGE "BOOT RECORD"
*= FMSORG

THE FOLLOWING BYTES ARE STORED
ON DISK SECTOR THEY COMPRISE

ATARI DOS 2.0S

07e0 00
eiei 03

07e2

0704
0706

0007
4015
4C1407

0709
070A
070B
070C

03
01
00
0115

07I3E 00

070F
0710
0711
0712

00
00
7D
CB07

2005
2006
2007
2008

2009

2010

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

2024

2025

2026

2027

2028

2029

2030

2031

2032

2033

2034

2035

THE BOOT LOAD RECORD

BFLG
BRCNT

.BYTE
.BYTE

BLDADR .WORD FMSORG
BINTADR .WORD DUPINIT
BCONT JMP XBCONT

;BOOT FLAG UNUSED=0
;N0 CONSECTIVE BOOT

READ
;B0OT LOAD ADDR
;INIT ADDR
;BOOT READ CONT PT

RECORDS TO

THE FOLLOWING BYTES ARE SET BY
■ THE CONSOLE PROCESSOR. THEY ARE
: ACTED UPON DURING FMS INIT ONLY,
r THEY ARE PART OF THE BOOT RECORD
; THUS DEFINING THE DEFAULT
[INITIALIZATION FARMS

SABYTE
DRVBYT
SAFBFW
SASA

.BYTE 3
.BYTE 01
.BYTE
.WORD ENDFMS

MAX # CONCURRENT OPEN FILES
DRIVE BITS

STORAGE ALLOCATION DIR SW
STORAGE ALLOCATION START ADDR

THE FOLLOWING CODE READS THE FMS
AND CONSOLE PROCESSOR (DOS) FROM
THE DOS. SYS FILE

DFSFLG .BYTE

; 00 NO DOS FILE

; 01 128 BYTE SECTOR

: 02 256 BYTE SECTOR

DFLINK .BYTE 0,0

2036 BLDISP

2037 DFLADR

2038 ;

2039 XBCONT
00714 AC0E07 2040

.BYTE
.WORD

125
DFMSDH

;DOS FLAG

DISK
DISK

;DOS FILE START SECTOR NUMBER

;DISPL TO SECTOR LINK
,-ADDR START OF DOS . SYS FILE

0717 F036

0719
071C
071E
0721

AD1207
8543
8D0403
AD1307
0724 8544
0726 8D0503

2041
2042
2043
2044
2045
2046
2047
2048
2049

LDY
BEQ

LDA
STA
STA
LDA
STA
STA

DFSFLG
BFAIL

DFLADR

ZBUFP

DCBBUF

DFLADR+1

ZBUFP+1

DCBBUF+1

;GET DOS
;BR IF NO

FLAG
DOS . SYS

MOVE LOAD START ADDR
TO ZERO PAGE PTR
AND TO DCB

BOOT RECORD

2050 ;

0729

AD1007

2051

LDA

DFLINK+1

;GET 1ST SECTOR #

072C

AC0F07

2052

LDY

DFLINK

072P

2053 XBCl

CLC

0730

AE0E07

2054

LDX

DFSFLG

;LOAD DISK TYPE COl

0733

206C07

2055

JSR

BSIO

;G0 READ BOOT SECT(

0736

3017

2056
2057 ;

BMI

BFAIL

07 38

AC1107

2058

LDY

BLDISP

; POINT TO LINK

07 3B

B143

2059

LDA

(ZBUFP)

;GET LINK HI

07 3D

2903

2060

AND

#LMASK

;MASK TO LINK BITS

0'i3F

2061

PHA

0740

2062

INY

0741

1143

2063

ORA

(ZBUFP)

0T43

F00E

2064

BEQ

BGOOD

0745

B143

2065

LDA

(ZBUFP)

;GET LINK LOW

0747

2066

TAY

ATARI DOS 2.0S

074H 205707

07411 68
074C 4C2F07

0741' A9C0
0751 D001

0753 68

0754 0A

0755 A8
07 56 60

0757
075EI
075;.
075D
0760
076::
076A
0766
076!i
07611

A543

6D1107

8D0403

8543

A544

6900

8D0503

8544

SECTOR I/O
076C

076C

076C 8D0B03

076F 8C0A03

0772 A952

0774 A040

0776 9004

0778 A950

077A A080

077C 8D0203
077F 8C0303

0782 A931
0784 A00F

0786 8D0003
0789 8C0603

078C A903
078E 8DFP12

0791 A900
0793 A080

0795 CA

0796 F004

0798 A901
079A A000

079C 8D0903

2067
2068 ;
2069
2070

2071 ;

2072 BFAIL
2073

2074 ;

2075 BGOOD

2076 ;

2077 XBRTN
2078

2079

2080 ;

2081 INCBA
2082

2083
2084
2085
2086
2087
2088
2089
2090
2091 ;

JSR INCBA

PLA
JMP

LDA
BNE

PLA

ASL
TAY
RTS

CLC
LDA
ADC
STA
STA
LDA
ADC
STA
STA
RTS

XBCl

#5C0
XBRTN

ZBUFP

BLDISP

DCBBUF

ZBUFP

ZBUFP+1

DCBBUF+1

ZBUFP+1

;G0 INCREMENT BUF ADR

; RESTORE LINK HI
;G0 READ NEXT SECTOR

;SET FOR CARRY SET
;ANY P,Y = $80

;SET FOR CARRY CLEAR

rlNC BUFFER PTR
;BY DATA LINK (125)

2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130

.PAGE "SECTOR I/O"
; BSIO - DO SECTOR I/O
BSIO = *

STA
STY

DCBSEC+1
DCBSEC

BSIOR LDA #DCBCRS

LDY #$40

BCC DSIOl

LDA #DCBCWS

LDY #$80

DSIOl

DSI02

STA DCBCMD

STY DCBSTA

LDA #$31

LDY #TIMOUT

STA DCBSBI
STY DCBTO

; SET SECTOR HI
; SECTOR LO

r ASSUME READ SECTOR
,-AND GET DATA
;BR IF READ

;ELSE LOAD WRITE SECTOR
;AND PUT DATA

;SET COMMAND
rAND SIO CMD

;DISK SERIAL BUS ID
.•TIMEOUT DEFAULT LOADED

LDA
STA

#3
RETRY

LDA
LDY
DEX
BEQ DSI03

#0
#$80

LDA
LDY

#1
#0

;SET ID

;SET TIME OUT

;SET RETRY COUNT

;ASSUME 128 BYTE
.•SECTOR DISK

;S0 BR

;ELSE IS 256

DSI03 STA DCBCNT+1 ; SET I/O BYTE CNT

ATARI DOS 2.0S

079F 8C0803

2131

2132 ;

2133 DSI04

STY

DCBCNT

07A2 2059E4

2134

JSR

$E459

07A5 101D

2135
2136 ;

BPL

DSI05

07A7 CEFF12

2137

DEC

RETRY

07AA 3018

2138
2139 ;

BMI

DSI05

7AC A240

2140

LDX

#$40

7AE A952

2141

LDA

#DCBCRS

07B0 CD0203

2142

CMP

DCBCMD

SIJCTOR I/O

07B3 F009

2143

BEQ

STRTYP

07B5 A921

2144

LDA

#DCBCFD

07B7 CD0203

2145

CMP

DCBCMD

07BA F002

2146

BEQ

STRTYP

07BC A280

2147

LDX

#$80

07£E 8E0303

2148 STRTYP

2149 ;

STX

DCBSTA

07C1 4GA207

2150
2151 ;

JMP

DSI04

07C4 AE0113

2152 DSI05

LDX

CURFCB

07C7 AD0303

2153

LDA

DCBSTA

07CA 60

2154
2155 ;

RTS

;CALL SERIAL I/O

;IF GOOD I/O THEN RTS

;TST IF ANOTHER RETRY AVAIL
;N0 THEN RTS WITH ERROR

DO RETRY-RESET TYPE ACTION
ASSUME READ-CK IF IS
IF COMMAND GET SECTOR

;YES THEN STORE GETSECTOR IN
;TEST IF FORMAT CMD
;IT ALSO RECIEVES DATA
rYES THEN SET AS GET DATA
;ELSE STORE PUTSECTOR

; RETRY THE l/O

; RELOAD CURRENT FCB

;AND I/O STATUS SET FLAGS

FILE MANGER ENTRY POINT

7CB

07CB AA08
07CD 140B
07CF BE0A
07D1 CB09
07D3 000B
07D5 A60B

07D7
7E0

Gi7E0 AD0C07

CI7E3 8543

CI7E5 AD0D07

CI7E8 8544

2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191

.PAGE "FILE MANGER ENTRY POINT"

; DFMSDH - DISK FILE MANAGEMENT DISK
; HANDLER ENTRY POINT

DFMSDH

.WORD DFMOPN-1 ;OPEN FILE

.WORD DFMCLS-1 ;CLOSE FILE

.WORD DFMGET-1 ;GET FILE

.WORD DFMPUT-1 ; PUT BYTE

.WORD DFMSTA-1 ; STATUS

.WORD DFMDDC-1 ;DEVICE DEPENDENT CMD

INITIALIZATION CODE

GIVE ROOM FOR BOOT EXPANSION 1 1 1

*= $7E0
DINIT = *

; SET UP DRIVE INFO

; DRVTBL - 8 BYTES-ONE FOR EACH POSSIBLE DRIVE

; = NO DRIVE

r 1 = 128 BYTE SECTOR DRIVE

r 2 = 256 BYTE SECTOR DRIVE

; DBUFA(L,H) 8 TWO BYTE ENTRYS THE

: DRIVE (VTOC) BUFFER ADR FOR A DRIVE

LDA SASA

STA ZBUFP

LDA SASA+1

STA ZBUFP+1

.-MOVE START OF ALLOC
;AREA TO ZBUFP

ATARI DOS 2.0S

07E*
07Er'

AD0A07
8D0C13

07Fe A207

07F2
07F5
07FE

07F*
07FC
07FF
0802
0805

8E0D13
0E0C13
B00D

A900

9D1113

9D2913

9D3113

F036

2192
2193
2194 ;
2195

2196 ;

2197 DIA
2198
2199
2200 ;
2201
2202
2203
2204
2205
2206 ;

LDA
STA

STX
ASL
BCS

LDA
STA
STA
STA
BEQ

DRVBYT
TEMPI

LDX #7

TEMP2
TEMPI
DIHAVE

DRVTBL.X

DBUFAL.X

DBUFAH.X

DIDDEC

;TEMP 1 IS DRIVE

; EXCESS BITS FROM BOOT

;TEMP 2 IS

;DR # MINUS 1

; SHIFT DR BIT TO CARRY

;BR IF DR EXISTS

DRVTBL.X ;SET NO DRIVE

;G0 DEC DRIVE #

FILE MANGER ENTRY POINT

0807 A005
0809 A900
080B 9143

080D E8
080E 8B0103
0811 A953
0813 8D0203
0816 2053E4

0819 A002
081B ADEA02
081E 2920

0820 D001
0822 88

0823
0824
082 7
082A
082C
082F
0831
0834

AE0D13

9D1113

A543

9D2913

A544

9D3113

207008

0837 88

0838 F003

083A 207008

083D CA
083E 10B2

0840 AC0907
0843 A200

0845 A900

2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255

DIHAVE

LDY #DVDWRQ ; SET WRITE READ OFF

LDA #0

STA (ZBUFP),Y ;IN THE DRIVE BUFFER

;PUT DR # IN DCB
;GET DRIVE STATUS

DI256

INX

STX

DCBDRV

LDA

#DCBCST

STA

DCBCMD

JSR

DHADR

LDY

LDA

$2EA

AND

#$20

BNE

DI256

PEY

TYA

LDX

TEMP2

STA

DRVTBL.X

LDA

ZBUFP

STA

DBUFAL.X

LDA

ZBUFP+1

STA

DBUFAH.X

JSR

DINCBP

DEY

BEQ

DIDDEC

JSR DINCBP

DIDDEC PEX

BPL DIA

.•ASSUME 256 BYTE DRIVE
;GET STATUS BYTE

,-BR IF 256

;SET DR TYPE INTO
;TBL AT DRIVE DISPL
;MOVE CURRENT ALLOC
;ADDR TO DBUFA
;AND INC ALLOC
rBY 128 BYTES
;VIA DINCBP

;IF DR WAS A

;128 BYTES THEN DONE

;ELSE INC PTR BY 128

;DEC DRIVE

;BR IF MORE TO TEST

SET UP SECTOR ALLOCATION TABLE

THE SECTOR ALLOCATION TABLE (SECTBL)
WAS 16 ONE BYTE ENTRIES ONE FOR
EACH POSSIBLE 128 BYTE BUFFER SABYTE
IN THE BOOT RECORD DETERMINES THE
NUMBER OF ENTRYS TO ALLOCATE
NON-ALLOCATED BYTE ARE MINUS

SABUF(L.H) CONTAINS THE ADDR OF THE SECTOR BUFFER

;GET AND SAVE COUNT

LDY SABYTE
LDX #0

DINXTS LDA #0

; ASSUME ALLOCATE

ATARI DOS 2.0S

01347 88 2256

0848 1001 2257
084A 98 2258

DEY ;DEC COUNT OF ALLOCATED

BPL DISETS ;IF PLUS STILL ALLOCATE
TYA ;ELSE DE ALLOCATE

FILE MANGER ENTRY POINT

2259

;

034B

9D1913

2260

DISETS

STA

SECTBL.X

,-SET ALLOCATE BYTE

0B4E

2261

TYA

;IF NO ALLOCATED

0B4F

300D

2262
2263

}

BMI

DISNI

;THEN DON'T ALLOC A'

0851

A543

2264

LDA

ZBUFP

rMOVE BUFFER ADDR

0B53

9D3913

2265

STA

SABUFL, X

;T0 SECTOR BUF PTR

0856

A544

2266

LDA

ZBUFP+1

0858

9D4913

2267

STA

SABUFH.X

085B

207008

2268
2269

JSR

DINCBP

!lNC SECTOR ADDR

085E

2270

DISNI

INX

;INC BUF #

085F

E010

2271

CPX

#16

;IF NOT ALL 16

0861

D0E2

2272
2273

BNE

DINXTS

;D0 AGAIN

2274

,- SET :

LOW MEM

2275

0863

A543

2276

LDA

ZBUFP

;MOVE FINAL ADDR

0865

8DE702

2277

STA

LMADR

.•TO LOW MEM PTR

0868

A544

2278

LDA

ZBUFP+1

086A

8DE802

2279
2280

;

STA

LMADR+1

086D

4C7E08

2281
2282

JMP

CLRFCB

;CONT INIT

2283

; DINCBP -

INC ZBUFP

BY 128

2284

;

e870

2285

DINCBP

CLC

e871

A543

2286

LDA

ZBUFP

e873

6980

2287

ADC

#128

e875

8543

2288

STA

ZBUFP

8877

A544

2289

LDA

ZBUFP+1

8879

6900

2290

ADC

e87B

8544

2291

STA

ZBUFP+1

e87D

2292
2293

RTS

2294

; CLEAR FCBS TO ZERO

2295

•

ei87E

2296

CLRFCB

ei87E

A07F

2297

LDY

#?7F

;128 OF FCB

CI880

A900

2298

LDA

(1882

998113

2299

CFCBX

STA

FCB.Y

;T0 BE CLEARED

0885

2300

DEY

0886

D0FA

2301
2302

;

BNE

CFCBX

FILE

MANGER

ENTRY

POINT

0B88

2303

.PAGE

2304

;

0888

A000

2305

LDY

088A

B91A03

2306

ADIl

LDA

DEVTAB.Y

;FIND AH

088D

F00C

2307

BEQ

ADI2

; UNUSED

088F

C944

2308

CMP

#'D

;0R DISK

0891

F008

2309

BEQ

ADI2

; EMPTY

0893

2310

INY

0894

2311

INY

0895

2312

INY

0896

C01E

2313

CPY

#30

0898

D0F0

2314

BNE

ADIl

089A

2315
2316

;

BRK

;ELSE BREAK

ATARI DOS 2.0S

089B A944

2317 ADI2 LDA #'D

089D ')91A03 2318
08A0 A9CB 2319
08A2 991B03 2320
08A5 A907 2321
08A7 991C03 2322
2323
08AA i50 2324

STA
LDA
STA
LDA
STA

RTS

;SET DISK

DEVTAB , Y
#DFMSDHS,2 55
DEVTAB+1,Y
#DFMSDH/2 56
DEVTAB+2 , y

rSET FMS ADDR

OPEN

08AB

2325

.PAGE "OPEN"

2326

;

2327

1 DFMOPN -

FILE OPEN

EXECUTION ENTRY PT

2328

;

2329

DFMOPN

08AB

206411

2330

JSR

SETUP

; DO FOB SET UP

08AE

209E0E

2331

JSR

FNDCODE

;G0 DECODE FILE NAME

08B1

BD4A03

2332

LDA

ICAUXl , X

; GET AUXl (OPEN TYPE CODES)

08B4

9D8213

2333

STA

FCBOTC.X

;PUT INTO FCB

08B7

2902

2334

AND

#OPDIR

; IS THIS LIST DIRECTORY

08B9

F003

2335

BEQ

OPNl

;BR IF NOT

08BB

4CAD0D

2336
2337

JMP

LISTDIR

;GOT0 DIR LIST CODE

08BE

20210F

2338

OPNl

JSR

SPDIR

;GO SEARCH FILE DIR

08C1

2339
2340

PHP

08C2

BD8213

2341

LDA

FCBOTC.X

;GET OPEN TYPE CODE

08C5

C904

2342

CMP

#OPIN

; INPUT

08C7

F00F

2343

BEQ

DFOIN

08C9

C908

2344

CMP

#OPOUT

r OUTPUT

08CB

F044

2345

BEQ

DFOOUT

08CD

C90C

2346

CMP

#OPIN+OPOUT ; UPDATE

08CF

F00C

2347

BEQ

DFOUPD

08D1

C909

2348

CMP

♦OPOUT+OPAPND ; APPEND

08D3

F017

2349

BEQ

DFOAPN

08D5

4CBF12

2350
2351

JMP

ERDVDC

TERROR

2352

; DFOIN - OPEN FOR INPUT

2353

;

08D8

2354

DFOIN

08D8

2355

PLP

;GET SEARCH FLAG

08D9

B00E

2356

BCS

OPNERl

; ERROR IP NOT FOUND

08DB

9006

2357
2358

BCC

DFOUI

2359

; DFOUPD -

OPEN FOR UPDATA

2360

;

08DD

2361

DFOUPD

08DD

2362

PLP

;GET SEARCH FLAG

08DE

B009

2363

BCS

OPNERl

rBR NOT FOUND

08E0

20AC0C

2364
2365

JSR

TSTLOCK

;TEST LOCK

08E3

2366

DFOUI

08E3

20AE09

2367

JSR

DFRDSU

;SET UP FOR READ

08Ee

4CF012

2368
2369

JMP

GREAT

rDONE

08E9

4CBB12

2370

OPNERl

JMP

ERFNF

;FILE NOT FOUND

OPEN

08EC

2371

.PAGE

2372

;

2373

; DFOAPN -

OPEN APPEND

2374

•

08EC

2375

DFOAPN =

08EC

: 28

2376

PLP

;GET READ STATUS

ATARI DOS 2.0S

0(iED
0(!EF
0HF2
0HF5
0HF7
0f)F9
0HFC
0f!FF
0902
0905
0908
090B
090E

B0FA

AC0513

B90114

2902

F015

20AC0C

20BF10

200611

9D8E13

BD8B13

9D8D13

4C7C09

4CB712

0911

0911 28

0912 B009

0914 20530C
0917 AC0513
091A 4C4809

09 ID

091D AD0213
0920 3070
0922 8D0613

0925
0928
092B
09 2 E
0931
0934
0937
093A
093C
093E

206E10

AD0313

8D0513

AD0413

8D0713

20BF10

AC0513

A20A

A920

990614

0'>41 C8

0942 CA

0943 10F9
0945 AE0113

0948

0948 200611

2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404

2405
2406
2407
2408
2409
2410
2411
2412
2413

BCS
LDY
LDA
AND
BEQ
JSR
JSR
JSR
STA
LDA
STA
JMP
APOER JMP

OPNERl ;BR NOT FOUND
CDIRD ;IF OLD.
FILDIR+DFDFLl,y ;FILE TYPE

#DFDNLD

APOER ;

TSTLOCK 1

OPVTOC ;

GETSECTOR i
FCBSSN+1,X

FCBLSN.X ;
FCBSSN.X

DHF0X2 )
ERAPO

THEN

ERROR

TEST LOCKED

READ VTOC

GET A SECTOR

;MOVE START SECTOR

TO START SECTOR #

CONTINUE AS OPEN

DFOOUT - OPEN FOR OUTPUT

DFOOUT =

PLP
BCS

JSR

LDY
JMP

DFOXl

LDA
BMI
STA

JSR
LDA
STA
LDA
STA
JSR
LDY
LDX
LDA

2414 OPNIB STA

2415
2416
2417
2418

2419 ;

2420 OPNIA =

2421 JSR

INY
DEX
BPL
LDX

DFOXl

XDEL0
CDIRD
OPNIA

DHOLES
0PNER2
CDIRS

RDDIR

DHOLED

CDIRD

DHFNUM

SFNUM

OPVTOC

CDIRD

#10

#$20

FILDIR+DFDPFN.Y

OPNIB
CURFCB

rGET SEARCH FLAG

; DELETE THE FILE OR FILES

;WAS THERE A HOLE

;BR IF NO HOLE

rSAVE HOLE SECTOR AS CURRENT

DIR SEC
;G0 READ CURRENT DIR SECTOR
jMOVE HOLE DISPL TO
;CUR DIR DISPL
;MOVE HOLE FN
;T0 CURRENT

jBLANK FILL FILE ENTRY
FOR FILE NAME

GETSECTOR ;GET A SECTOR

OPEN

094B

AC0513

2422

LDY

034E

990514

2423

STA

0951

BD8B13

2424

LDA

0954

990414

2425
2426 ;

STA

0957

A943

2427

LDA

0959

990114

2428

STA

095C

A900

2429

LDA

095E

990314

2430

STA

0')61

990214

2431
2432 ;

STA

0964

A200

2433

LDX

0!)66

BD5913

2434 0PN2

LDA

0969

C93F

2435

CMP

096B

F003

2436

BEQ

CDIRD ;GET DIR DISPL
FILDIR+DFDSSN+1,Y ; PUT SECTOR INTO DIR

REC
FCBLSN.X
FILDIR+DFDSSN.Y

#DFDINU+DFDOUT+DFDNLD ;SET DIR ENTRY IN

USE
FILDIR+DFDFL1,Y
#0 ; SET NOT LOCKED
FILDIR+DFDCNT+1,Y ;SET COUNT =
FILDIR+DFDCNT,Y

FNAME,X ;MOVE FILE NAME

*'? rIF WILD CARD

0PN2A ; CHANGE TO BLANK

ATARI DOS 2.0S

096D

990614

2437

STA

FILDIR+DFDPFN.Y ;T0 DIRECTORY

0970

2438

0PN2A

0970

2439

INY

0971

2440

INX

0972

E00B

2441

CPX

#11

0974

90F0

2442
2443

BCC

0PN2

0976

AE0113

2444

LDX

CURFCB

; RESTORE X REG

0979

207110

2445

JSR

WRTDIR

;G0 WRITE DIRECTORY

09 7C

2446

DHF0X2

097C

209509

2447

JSR

SETFCB

097F

20E20F

2448

JSR

WRTN6

;FIX UP AS IF WRITE

0982

A980

2449

0PN3

LDA

#FCBFAS

;SET NEW FILE

0984

9D8513

2450

STA

FCBFLG.X

0987

209B12

2451

JSR

TSTDOS

rIF NOT DOS

098A

D003

2452

BNE

DHF0X3

rBR

098C

4C0A12

2453

JMP

WRTDOS

;ELSE DO IT

098F

2454

DHF0X3

098F

4CF012

2455
2456

JMP

GREAT

0992

20BD12

2457
2458
2459

0PNER2

JSR

ERDFULL

.•DIRECTORY FULL

0995

2460

SETFCB

0995

A900

2461

LDA

; CLEAR

0997

9D8513

2462

STA

FCBFLG.X

;FLAG

099A

AD0713

2463

OPNFl

LDA

SPNUM

;MOVE FILE NUM TO FCB

099D

2464

ASL

099E

2465

ASL

099F

9D8113

2466

STA

FCBFNO.X

09A2

A900

2467

LDA

09A4

9D8713

2468

STA

FCBDLN.X

;DATA LENGTH

09A7

9D8F13

2469

STA

FCBCNT.X

;SET CNT =

09AA

9D9013

2470

STA

FCBCNT+1 ,

09AD

2471

RTS

09AE

209509

2472

DFRDSU

JSR

SETFCB

,-SET UP FCB

09B1

AC0513

2473

LDY

CDIRD

;MOVE START SECTOR TO LINK

OPEN

09B4

B90114

2474

LDA

DFDFLl+FILDIR.Y ;SET NEW

09B7

2902

2475

AND

♦DFDNLD

; SECTOR

09B9

9D8413

2476

STA

FCBSLT.X

;FLAG

09BC

B90414

2477

LDA

FILDIR+DFDSSN.Y

09BF

9D8B13

2478

STA

FCBLSN.X

09C2

B90514

2479

LDA

FILDIR+DFDSSN+1 . Y

09C5

9D8C13

2480

STA

FCBLSN+1 ,

09C8

201710

2481

JSR

RDNSO

;READ 1ST SECTOR

09CB

2482

RTS

09CC

.INCLUDE #E!

09CC

.INCLUDE #DiATFMS2.SRC

PUT EIYTE

09CC

3000

.PAGE "PUT BYTE"

3001

3002

r DFMPUT -

PUT A FILE

BYTE

3003

3004

DFMPUT

09CC

8D0813

3005

STA

SVDBYT

09CF

BD4103

3006

LDA

ICDNO.X

09D2

8521

3007

STA

ICDNO-IOCB+ZICB

09D4

206411

3008

JSR

SETUP

09D7

AC0013

3009

LDY

ENTSTK

;CHK TO SEE IF ENTRY WASN'T
FROM CIO

09DA

B90201

3010

LDA

STAK.Y

;IF HI BYTE RTS IS NOT IN OS
ADDR

ATARI DOS 2.0S

09I)D C9DF 3011
09I)F B004 3012
09I!1 A900 3013

09Ii3
091! 5
09i:8
09I!A
09I!C
091!F
091'0
09!''3
09F5
09)'8
091-'A
091?D
091?F
0A01
0AI93

8522

BD8213

2908

F02D

BC8713

DD8613

9011

20940F

B022

201F0A

A000

B005

B124

8D0813

0AI36 FE8713
0A09 AD0813
0Ai3C 9147

0AI2IE A940
0A10 1D8513
0A13 9D8513

0A16 4CF012

0A19 4CBF12
0AIC 4CF412

3014

3015 FRMCIO

3016

3017

3018

3019

3020

3021

3022

3023

3024

3025

3026

3027

302B

3029 ;

3030 PUTl
3031
3032
3033 ;
3034
3035
3036
3037 ;
3038

3039 ;

3040 PUTER

3041 PEOF

CMP
BCS
LDA

STA
LDA
AND
BEQ
LDY
TYA
CMP
BCC
JSR
BCS
JSR
LDY
BCS
LDA
STA

INC
LDA
STA

LDA
ORA

STA

#OSBTM ; SPACE THEN A NON-CIO ENTRY

FRMCIO ;BR IF FROM CIO

#0 ;ELSE PREVENT FROM DOING BURST

I/O
ICCOMZ

FCBOTC.X ;IF NOT OPEN

#OPOUT ; OUTPUT

PUTER ; ERROR

FCBDLN.X ;GET DATA LENGTH

FCBMLN.X ;IF SECTOR NOT FULL

PUTl ;THEN BR

WRTNXS ;ELSE WRITE FULL SECTOR

PEOF ;BR IF EOF

WTBUR rTEST BURST

PUTl ;BR IF NOT BURST

(ICBALZ),Y ;PUT NEXT BYTE

SVDBYT rAFTER BURST AREA

FCBDLN.X ;INC DATA LEN

SVDBYT ;GET DATA BYTE

(ZSBA),Y ;AND PUT IN SECTOR BUFFER

#FCBFSM

FCBFLG.X

! INDICATE SECTOR MODIFIED

JMP GREAT

JMP
JMP

ERDVDC
ERREOF

BURST I/O
0A1F

0S1F BD8513
0A22 1026
0A24 3002

0;>26 A900

0?.28 8D1013
0?.2B A522
0;i.2D 2902
0?.2F F019

0;31 20AE0A
0J.34 B014

0;l36 A524
0A38 8547
0;l3A A525
0;l3C 8548

0A3E AD1013
0A41 3009

0A43 200F10
0A46 9033
0A48 B053

0iUA 38
0iUB 60

3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073

.PAGE "BURST I/O"
; TEST BURST l/O AND DO IF POSSIBLE
WTBUR

LDA
BPL
BMI

FCBFLG.X

NOBURST

TBURST

RTBUR LDA #0

TBURST STA BURTYP

LDA ICCOMZ

AND #2

BEO NOBURST

JSR TBLEN

BCS NOBURST

LDA ICBALZ

STA ZSBA

LDA ICBAHZ

STA ZSBA+1

NXTBUR LDA BURTYP

BMI WRBUR

JSR RDNXTS

BCC BBINC

BCS BUREOF

NOBURST SEC
RTS

;IF NOT AQUIRING SECTORS
.-THEN UPDATE AND
;NO BURST

rSET READ TYPE

•SET BURST TYPE
;IF CMD
;IS TEXT MODE
;THEN NO BURST

;IF USER BUFFER LESS
;THEN SECTOR, NO BURST

;MOVE USER BUFFER
;ADDR TO SECTPOR
; BUFFER PTR

;GET I/O TYPE
;BR IF WRITE

J DO SECTOR READ
;BR IF EOF
;BR RD EOF

; INDICATE NO BURST

AT/iRI DOS 2.0S

3074 ;

0A4C

ADF812

3075 WRBUR

LDA

DRVMDL

;WRITE FULL SECTOR

0A4F

9D8713

3076
3077 ;

STA

FCBDLN,

;DATA COUNT

0A52

3078

TAY

0A53

B147

3079

LDA

(ZSBA),

rSAVE DATA TO BE

0A55

8D0913

3080

STA

SVDl

;T0 BE CLOBBERED

0A58

3081

INY

0A59

B147

3082

LDA

(ZSBA),

;BY WRTNXT

0A5B

8D0A13

3083

STA

SVD2

0A5E

3084

INY

0A5F

B147

3085

LDA

(ZSBA),

0A61

8D0B13

3086
3087 ;

STA

SVD3

0A64

20940F

3088
3089 ;

JSR

WRTNXS

;WRITE SECTOR

0A67

ACF812

3090

LDY

DRVMDL

; RESTORE CLOBBERED DAI

0AeA

AD0913

3091

LDA

SVDl

0A6D

9147

3092

STA

(ZSBA),

BURST I/O

0A6F

3093

INY

0A70

AD0A13

3094

LDA

SVD2

0A73

9147

3095

STA

(ZSBA)

0A75

3096

INY

0A76

AD0B13

3097

LDA

SVD3

0A79

9147

3098

3099 ;

3100 ;

STA

(ZSBA)

0A7B

3101 BBINC

CLC

0A7C

A547

3102

LDA

ZSBA

;INC SECTOR

0A7E

7D8613

3103

ADC

FCBMLN

; BUFFER ADDR BY

0A81

8547

3104

STA

ZSBA

; ACTUAL DATA LEN

0A83

A548

3105

LDA

ZSBA+1

;GOT OT PUT

0A85

6900

3106

ADC

0A87

8548

3107
3108 ;

STA

ZSBA+1

0A89

3109

SEC

0A8A

A528

3110

LDA

ICBLLZ

;DEC USER

0A8C

FD8613

3111

SBC

FCBMLN

; BUFFER LEN BY

0A8F

8528

3112

STA

ICBLLZ

; ACTUAL DATA LEN

0A91

A529

3113

LDA

ICBLHZ

;GOT OR PUT

0A93

E900

3114

SBC

0A95

3115

NOP

0A96

8529

3116
3117 ;

STA

ICBLHZ

0A98

20AE0A

3118

JSR

TBLEN

,-IF USER BUF LEN

0A9B

90A1

3119
3120 ;

BCC

NXTBUR

;NOW >= SECTOR, DO AG

0A9D

3121 BUREOF

;END OF BURSTING

0A9D

A547

3122

LDA

ZSBA

;MOVE FINAL ADDR BACK

0A9F

8524

3123

STA

ICBALZ

;T0 USER BUF PTR

0AA1

A548

3124

LDA

ZSBA+1

0AA3

8525

3125
3126 ;

STA

ICBAHZ

0AA5

BC8813

3127

LDY

FCBBUF

; RESTORE ZSBA

0AA8

3128

DEY

0AA9

20D011

3129
3130 ;

JSR

SSBA

0AAC

3131 BURST

CLC

0AAD

3132
3133 ;

RTS

3134 ,- TEST

USER

BUF LEN FOR BURST

3135 ;

0AAE

3136 TBLEN

= .

0AAE

ADFE12

3137

LDA

DRVTYP

;IF DRIVE NOT

ATARI DOS 2.0S

0AE1

C901

3138

CMP

;128 BYTE SECTOR TYPE

0AEi3

D004

3139
3140 !

BNE

TBL256

;THEN DO 256 BYTE TEST

0AE;5

A528

3141

LDA

ICBLLZ

0AEi7

30F3

3142
3143

BMI

BURST

0AEI9

A529

3144 TBL256

LDA

ICBLHZ

;IF BUF LEN HI >= 256

BUBST

I/O

0AEB

D0EF

3145

BNE

BURST

;THEN CAN BURST

0AE;D

3146

SEC

0AE:E

3147

RTS

GET BYTE

0AI1F

3148

.PAGE "GET BYTE"

3149

3150

3151

DFMGET -

SET A FILE

BYTE

3152

0AI1F

3153 I

3FMGET

0ABF

206411

3154

JSR

SETUP

;G0 SET UP

0AC;2

BD8213

3155

LDA

FCBOTCX

rIF OPEN FOR

0A<;5

2902

3156

AND

#OPDIR

;DIR CNT

0A<;7

F003

3157

BEQ

GETl

0A(;9

4CB90D

3158
3159

JMP

GDCHAR

;THEN GO TO DIR RTN

0A(:c

BD8713

3160

3ET1

LDA

FCBDLN.X

;GET DATA LEN

0a(:f

DD8613

3161

CMP

FCBMLN.X

;TEST EMPTY SECTOR

0A132

900B

3162

BCC

GET 2

;BR IF NOT EMPTY

0A154

20260A

3163

JSR

RTBUR

;D0 BURST IF POSSIBLE

0A1)7

200F10

3164

JSR

RDNXTS

;GET NEXT SECTOR

0A1)A

90F0

3165

BCC

GETl

;BR IF NOT EOF

0A1X:

3166

3E0F

0A1X;

4CF412

3167
3168

•

JMP

ERREOF

;ELSE EOF ERROR

0ADF

3169

SET2

TAY

0AK0

B147

3170

LDA

(ZSBA),Y

;GET DATA BYTE

0a:52

8D0813

3171

STA

SVDBYT

rSAVE THE BYTE

0a:35

3172

INY

0A:Ee

3173

TYA

0a:e7

9D8713

3174

STA

FCBDLN.X

;AND SET NEW VALUE

0AEA

3175

EFLOOK

0AEA

BC8B13

3176

LDY

FCBLSN.X

;D0 EOF LOOK AHEAD

0AED

D00F

3177

BNE

GET 3

;IF LSN NOT ZERO

0AEF

BC8C13

3178

LDY

FCBLSN+1 ,

X ;THEN

0AF2

D00A

3179

BNE

GET 3

;NOT EOF

0AF4

DD8613

3180

CMP

FCBMLN.X

;IF LSN=0 THEN CHECK F

0AF7

9005

3181

BCC

GET 3

;LAST BYTE

0AF9

A903

3182

LDA

#503

;IF LAST BYTE THEN RTS

00\FB 4CD312 3183

JMF

RETURN

3184

;

0AFE

4CF012

3185

GET3

JMP

GREAT

STATUS

0B01

3186

.PAGE "STATU

3187

;

3188

; DFMSTA -

GET A FI

3189

;

3190

DFMSTA

01301

206411

3191

JSR

SETUP

01304

209E0E

3192

JSR

FNDCODE

01307

20210F

3193

JSR

SFDIR

0130A

B006

3194

BCS

SFNF

FILE STATUS

; SETUP

; DECODE FILE NAME
; SEARCH FOR FILE
;BR NOT FOUND

ATARI DOS 2.0S

0B0C

20AC0C

3195

JSR

TSTLOCK

0B0F

4CF012

3196
3197

JMP

GREAT

0B12

4CBB12

3198

SFNF

JMP

ERFNF

;TEST LOCKED

;FILE EXISTS AND UNLOCKED

close;

0B15

0B15 206411
0B18 Bn8213
0B1B 2908
0B1D F04E

0B1F 3E8513
0B22 9051

0B24 20AB0F

0B27 20800B
0B2A BD9013
0B2D 48
0B2E BD8F13
0B31 48

0B32 BD8213
0B35 2901
0B37 F017

0B39 20AE09
0B3C 200F10
0B3F 90FB

0B41 BD8D13
0B44 9D8B13
0B47 BD8E13
0B4A 9D8C13
0B4D 20B30F

0B50 AC0513
0B53 18
0B54 68
0B55 790214
0B58 990214
0B5B 68
0B5C 790314
0B5F 990314

0B62 A942
0B64 990114
0B67 207110
0B6A 209510

0B6D A900
0B6F 9D8213

3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249

.PAGE "CLOSE"

DFMCLOSE

CLOSE A FILE

DFMCLS

JSR
LDA
AND
BEO

ROL
BCC

APPl

CLOUT

LDA
STA
LDA
STA
JSR

LDY
CLC
PLA
ADC
STA
PLA
ADC
STA

LDA
STA
JSR
JSR

CLDONE LDA
STA

SETUP
FCBOTCX
#OPOUT
CLDONE

FCBFLG.X
CLUPDT

;GET OPEN CODE
;IF NOT OUTPUT
;THEN DONE

;IF NOT ACQUIRING SECTORS
;THEN IS UPDATE

JSR WRTLSEC

RRDIR
FCBCNT+1 , X

;WRITE LAST SECTOR

GO GET DIRECTORY
;GET CNT OF SECTORS

JSR

LDA

PHA

LDA FCBCNT.X

PHA

LDA FCBOTC.X ;GET OPEN CODE
AND #OPAPND ;IF NOT APPEND
BEQ CLOUT ;BR

JSR DFRDSU
JSR RDNXTS
BCC APPl

;ELSE SET UP FOR READ
;READ TO EOF

FCBSSN.X rMOVE START SECTOR

FCBLSN.X TO EOF LINK SECTOR

FCBSSN+1,X

FCBLSN+1,X

WRTN2 ;THEN WRITE AS NOT EOF

CDIRD

;GET DIR DISPL

FILDIR+DFDCNT.Y
FILDIR+DFDCNT.Y

FILDIR+DFDCNT+l,y
FILDIR+DFDCNT+1,Y

#DFDINU+DFDNLD ;SET ENTRY TO IN USE
FILDIR+DFDFLl.Y
WRTDIR ;WRITE DIR
WRTVTOC .-WRITE VTOC

*0
FCBOTCX

; CLEAR OPEN CODE

0B72 4CEA12 3250

3251 ;
0B75 3252 CLUPDT
0B75 3E8513 3253
0B78 90F3 3254

JMP FGREAT

ROL
BCC

FCBFLG.X
CLDONE

;IF SECTOR NOT MODIFIED
;THEN DONE

ATARI DOS 2.0S

0B7A 20F80F 3255

0B7D 4C6D0B 3256

3257

JSR WRCSIO
JMP CLDONE

;ELSE WRITE IT
; THEN DONE

0Bf!0

3258

.PAGE

3259

;

3260

; RE-READ DIR RECORD

3261

;

0B(i0

3262

RRDIR

0B(!0

3D8113

3263

LDA

FCBFNO.X

0BH3

3264

LSR

0BB4

3265

LSR

0Bf)5

8D0713

3266
3267
3268

;

STA

SFNUM

0Bf)8

209B0B

3269

JSR

FNSHFT

03 »B

8D0613

3270

STA

CDIRS

0BBE

209B0B

3271

JSR

FNSHFT

0B<»1

209D0B

3272

JSR

FNSHFl

0B!>4

3273

ASL

0B95

8D0513

3274
3275

;

STA

CDIRD

0B<)8

4C6E10

3276

JMP

RDDIR

0BI>B

A900

3277

FNSHFT

LDA

0BI»D

A003

3278

FNSHFl

LDY

0B9F

1E8113

3279

FNSHF2

ASL

FCBFNO.X

03 A 2

3280

ROL

0BA3

3281

DEY

0BiV4

D0F9

3282

BNE

FNSHF2

0Bi\6

3283

RTS

•GET FILE NUMBER

;SET ACU=FILE NO/64
;T0 GET DIR SECTOR
;SET ACU TO REM=16

;T0 GET DIR DISPL

; SHIFT 3 BITS OF
;FILE NO INTO ACU

DEVICE DEPENDENT COMMAND

03 A 7

0BA7
0B.\A
0BAD
0BAF
03 Bl
03B3
0BB5
03 B6
0B38
0BBA
03 BB
03 BC
03 BF
03 C0
03C3
0BC4

206411

3D4203

C9FE

F025

C927

B01E

E920

9019

B9C50B

B9C60B

03C5
0BC7
0BC9
0BCB
03CD
03CF
0BD1

0027

0BD8
0C31
0BD2
0C7B
0C82
0C39
0D02

3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315

.PAGE "DEVICE DEPENDENT COMMAND"

DFMDDC - DEVICE DEPENDENT CMD EXECUTION

JSR
LDA
CMP
3EQ
CMP
3CS
SEC
SBC
BCC
ASL
TAY
LDA
PHA
LDA
PHA
RTS

SETUP

ICCOM.X

#254

XFV

♦MAXDDC

DVDCER

#S20

DVDCER

DVDCVT.Y

DVDCVT+1 , Y

;SET UP FOR EXECUTION

;GET COMMAND

;IS IT FORMAT

;BR IF

;TEST RANGE

;BR OUT OF RANGE

; SUBTRACT BASE OF CMDS
,-3R OUT OF RANGE

.-PUSH EXECUTION ADDR

. D3YTE XRENAME-1 ; 20-RENAME
. DBYTE XDELETE-1 ;21-DELETE
. DBYTE DVDCER-1 ; INVALID CMD
.DBYTE XLOCK-1 ;23-LOCK
.DBYTE XUNLOCK-1 ; 24-UNLOCK
. DBYTE XPOINT-1 ;25-POINT
.DBYTE XNOTE-1 ; 26-NOTE

MAXDDC

S27

;MAX DVDC+1

ATARI DOS 2.0S

3316 ;
0BD3 4CBF12 3317 DVDCER JMP ERDVDC
0BD6 4C180D 3318 XFV JMP XFORMAT

; FORMAT VECTOR

RENAWE

0BD9

0BD9 209E0E
0BDC 8C0D13
0BDF 20210F
0BE2 9003
0BE4 4CBB12

0BE7 20AC0C
0BEA 209B12
0BED D003
0BEF 201912

.PAGE "RENAME"
XRENAME - RENAME A FILE OR FILES

0BF2
0BF5
0BF8
0BFB
0BFD
0C00
0C03
0C04
0C07
0C08
0C09

AC0D13

20B40E

209B12

D00F

AC0513

B90514

B90414

205312

0C0C A200
0C0E AC0513

0C11 BD5913
0C14 C93F
0C16 F003
0C18 990614

0C1B C8
0C1C E8
0C1D E00B
0C1F 90F0
0C21 AE0113

0C24 207110

0C27 209E0E
0C2A 20310F
0C2D 90B8

0C2F 4CEA12

3319

3320

3321

3322

3323 XRENAME

3324

3325

3326

3327

3328

3329 ;

3330 XRNl
3331
3332
3333

3334 XRNIA
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345

3346 ;

3347 XRNIB
3348
3349

3350 ;

3351 XRN2
3352
3353
3354

JSR
STY
JSR
BCC

JMP

JSR
JSR
BNE
JSR

LDY
JSR
JSR
BNE
LDY
LDA
PHA
LDA
TAY
PLA
JSR

LDX
LDY

LDA
CMP
BEQ
STA

3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367

XRN3

FNDCODE

TEMP2

SFDIR

XRNl

ERFNF

TSTLOCK
TSTDOS
XRNIA
DELDOS

TEMP2

FNDCNX

TSTDOS

XRNIB

CDIRD

FILDIR+DFDSSN+1 , Y

FILDIR+DFDSSN.Y

;A,Y NEW DOS

; DECODE FILE NAME
;SAVE FNAME INDEX
;GO FINE FILE IN DIR
;BR IF FOUND

;TEST LOCK

; IF NOT DOS

fTHEN

; DON'T CHANGE SO

;GET INDEX FOR END FNl
;G0 DECODE NEXT FILE NAME
;IF NOT DOS
;THEN

SETDSO

rGO WRITE SECTOR ZERO

#0
CDIRD

FNAME, X ;MOVE FILE NAME
#'7 ;FROM FNAME TO DIR ENT
XRN3 ;BUT DON'T CHANGE WILD CARD
FILDIR+DFDPFN,Y ;CHARS INDICATED IN
FNAME

INY

INX

CPX #11

BCC XRN2

LDX CURFCB

JSR WRTDIR

JSR FNDCODE

JSR CSFDIR

BCC XRNl

JMP FGREAT

; RESTORE X-REG

;G0 WRITE CIR DIR RECORD

;GET OLD FILENAME AGAIN
;CONTINUE SEARCH OF DIR
;BR IF FOUND ANOTHER

fGO TO GOOD ENDING

.PAGE "DELETE"

DELETE

0C32 3368

3369 ;

3370 ; XDELETE - DELETE ALL FILENAMES THAT MATCH

3371 ;

3372 XDELETE
0C32 209E0E 3373 JSR

0C35 20210F 3374

JSR

FNDCODE
SFDIR

;G0 DECODE FILENAME

r SEARCH DIR FOR FILENAME

ATARI DOS 2.0S

0C38

B03F

3375

BCS

DFNF

0C3A

3376

XDELX

0C3A

20530C

3377

JSR

XDEL0

0C3D

209B12

3378

JSR

TSTDOS

0C40

D003

3379

BNE

XDELY

0C42

201912

3380
3381
3382

XDELY

JSR

DELDOS

0C45

207110

3383

XDEL3

JSR

WRTDIR

0C48

20310F

3384

JSR

CSFDIR

0C4B

90ED

3385

BCC

XDELX

0C4D

209510

3386

JSR

WRTVTCX:

0C50

4CEA12

3387
3388

JMP

FGREAT

0C53

20BF10

3389
3390

XDEL0

JSR

OPVTOC

0C56

AC0513

3391

XDELl

LDY

CDIRD

0C59

20AC0C

3392

JSR

TSTLOCK

0C5C

A980

3393

LDA

tDFDEDE

0C5E

990114

3394
3395

STA

FILDIR+DFl

0C61

20AE09

3396

JSR

DFRDSU

0C64

4C6C0C

3397
3398

JMP

XDEL2A

0C67

200F10

3399

XDEL2

JSR

RDNXTS

0C6A

B006

3400

BCS

XDEL4

0C6C

3401

XDEL2A

0C6C

20C510

3402

JSR

FRESECT

0C6F

4C670C

3403
3404

JMP

XDEL2

0C72

3405

XDEL4

0C72

A005

3406

LDY

#DVDWRQ

0C74

A9FF

3407

LDA

#$FF

0C76

9145

3408

STA

(ZDRVA),Y

0C78

3409
3410

RTS

0C79

4CBB12

3411

DFNF

JMP

ERFNF

;BR NOT FOUND

WRITE DIR ENTRY
LOOK FOR NEXT MATCH
BR IF FOUND

;GET DIR DISPL
;G0 TEST LOCK
;LOAD DELETED FLAG
FL1,Y rDELETE FILE

;READ NEXT SECTOR

;FREE CURRENT SECTOR

rTURN ON WRITE REQ ' D

;FILE NOT FOUND

UCK AND UNLOCK

0c:7c

3412

.PAGE "LOCK AND

UNLOCK"

3413

•

3414

; XLOCK - LOCK A FILE

3415

; XUNLOCK -

UNLOCK A FILE

3416

3417

XLOCK

0<:7C

A920

3418

LDA

tDFDLOC

r SET LOCK

0<:7E

8D0F13

3419

STA

TEMP4

0(:81

D005

3420

BNE

XLCOM

•GO TO COMMON

3421

XUNLOCK

0C83

A900

3422

LDA

:SET UNLOCK

0<:85

8D0F13

3423
3424

STA

TEMP4

0(:88

209E0E

3425

XLCOM

JSR

FNDCODE

; DECODE FILE NAME

0<:8B

20210F

3426

JSR

SFDIR

;FIND 1ST MATCH

0C8E

9003

3427

BCC

XLCl

rBR MATCH FOUND

0(:90

4CBB12

3428
3429

JMP

ERFNF

;BR NOT FOUND

0(:93

AC0513

3430

XLCl

LDY

CDIRD

;GET CURRENT DISPL

0C96

B90114

3431

LDA

FILDIR+DFDFLl.Y ;GET LOCK BYTE

0(:99

29DF

3432

AND

#$DF

rTURN OFF LOCK

0C9B

0D0F13

3433

ORA

TEMP4

;0R IN LOCK/UNLOCK

0C9E

990114

3434

STA

FILDIR+DFDFLl.Y rSET NEW LOCK

0(:ai

207110

3435
3436

JSR

WRTDIR

;G0 WRITE

0CA4

20310F

3437

JSR

CSFDIR

;LOOK FOR NEXT MATCH

0CA7

90EA

3438

BCC

XLCl

;BR FOUND

ATARI DOS 2.0S

0CA9 4CEA12 3439 JMP FGREAT ;ELSE DONE

3440 ;

3441 ; TSTLOCK - TEST FILE LOCKED

3442 ;

3443 TSTLOCK
0CAC AC0513 3444 LDY
0CAF B90114 3445 LDA
0CB2 2920 3446 AND
0CB4 D001 3447 BNE
0CB6 60 3448 RTS

3449 ;
0CB7 4CC112 3450 TLF JMP ERFLOCK

CDIRD ;GET DIR DISPL
FILDIR+DFDFLl.Y ;LOAD LOCK BYTE
♦DFDLOC ;MASK LOCK BIT
TLF ;BR IF LOCKED

POINT

0CBA

3451

.PAGE "POINT"

3452

•

3453

; XPOINT -

POINT REQUEST

3454

;

3455

XPOINT

0CBA

BD8513

3456

LDA

FCBFLG,X

;IF ARQ SECTORS

0CBD

3041

3457

BMI

PERRl

; POINT INVALID

0CBF

BD4D03

3458

LDA

ICAUX4,X

;IF REQUEST IS NOT

0CC2

DD8A13

3459

CMP

FCBCSN+1 ,

X ;SAME AS CURRENT

0CC5

D008

3460

BNE

XPl

;THEN BR

0CC7

BD4C03

3461

LDA

ICAUX3,X

0CCA

DD8913

3462

CMP

FCBCSN.X

0CCD

F01E

3463
3464

;

BEQ

XP2

jELSE NO NEED TO CI

0CCF

BD8513

3465

XPl

LDA

FCBFLG.X

;IF NOT MODIFIED

0CD2

F008

3466

BEQ

XPIA

;BR

0CD4

20P80F

3467

JSR

WRCSIO

;ELSE WRITE IT

0CD7

A900

3468

LDA

0CD9

9D8513

3469

STA

FCBFLG.X

0CDC

3470

XPIA

0CDC

BD4D03

3471

LDA

ICAUX4,X

0CDF

9D8C13

3472

STA

FCBLSN+1,

0CE2

BD4C03

3473

LDA

ICAUX3,X

0CE5

9D8B13

3474

STA

FCBLSN.X

0CE8

201710

3475

JSR

RDNSO

;READ REQ SECTOR

0CEB

B00A

3476
3477

BCS

XPERR

0CED

BD4E03

3478

XP2

LDA

ICAUX5,X

;TEST REQ DATA LEN

0CF0

DD8613

3479

CMP

FCBMLN.X

;LESS THEN MAX

0CF3

9005

3480

BCC

XP3

0CF5

F003

3481

BEQ

XP3

0CF7

3482

XPERR

0CF7

4CC312

3483
3484

JMP

ERRPDL

;IF NOT THEN ERROR

0CFA

9D8713

3485

XP3

STA

FCBDLN.X

;SET NEW DATA LEN

0CFD

4CF012

3486
3487

;

JMP

GREAT

0D00

4CB912

3488

PERRl

JMP

ERRPOT

0D03

3489

.PAGE "NOTE"

3490

;

3491

; XNOTE - EXECUTE NOTE

REQUEST

3492

;

3493

XNOTE

0D03

BD8713

3494

LDA

FCBDLN.X

fDATA LENGHT VALUE

0D06

9D4E03

3495

STA

ICAUX5,X

;T0 AUX 2

0D09

BD8913

3496

LDA

FCBCSN.X

;CUR SEC NO (LO)

0D0C

9D4C03

3497

STA

ICAUX3.X

J TO AUX 3

0D0F BD8A13 3498

LDA FCBCSN+1. X ;CUR SEC NO (HI)

ATARI DOS 2.0S

0D:.2 9D4D03 3499
0d:.5 4CF012 3500

STA
JMP

ICAUX4,X
GREAT

;T0 AUX 4

P01«1AT
0D:L8

3501

.PAGE "FORMAT"

3502 ;

3503 ; XFORMAT

3504 ;

3505 XFORMAT

0D18
0DIA
0DLD
0DLF
0D22
0D:24
00 27
0D29
0D2C
0D2F
0D31
0D34

0d:)7 1019

0D;)9 C090

0d:)B D012

0D:iD

0D3D A000

0D:JF B147

0D41 C9FF

0D43 D007

0D45 C8

0D46 B147

0D48 C9FF

0DIA F003

0DtC 4CB512

0DtF 4CD312

0D52 A900
0D54 A8
0D55 9145
0D57 C8
0D58 10FB

0D5A
0D5C
0D5E
0D60
0DS1
0D63
0D65
0D66
0D67

A000

A902

9145

A9C3

9145

FORMAT A DISKETTE

A548

8D0503

A547

8D0403

A921

8D0203

A940

8D0303

AEFE12

A931

AC4602

208607

3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517

3518 ;
3519
3520
3521

3522 ;

3523 TSTFMT
3524

3525
3526
3527
3528
3529
3530
3531

3532 XFBAD

3533 ;

3534 XFERR

3535 ;

3536 XF0
3537
3538

3539 XFl
3540
3541
3542 ;
3543
3544
3545
3546
3547
3548
3549
3550
3551

LDA
STA
LDA
STA
LDA
STA
LDA
STA
LDX
LDA
LDY
JSR

BPL
CPY
BNE

LDY
LDA
CMP
BNE
INY
LDA
CMP
BEQ
JMP

LDA
TAY
STA
INY
BPL

LDY
LDA
STA
INY
LDA
STA
INY
INY
STA

ZSBA+1

DCBBUF+1

ZSBA

DCBBUF

♦DCBCFD

DCBCMD

#$40

DCBSTA

DRVTYP

#$31

DSKTIM

DSI02

XF0

#$90
XFERR

(ZSBA),Y
#$FF
XFBAD

(ZSBA),Y
#$FF
XFERR
ERDBAD

;MOVE VTOC BUF ADR
;T0 DCB

J FORMAT
;T0 DCB
;TELL SIO RECIEVING DATA

;GET DR TYPE 128 OR 256
jBUS I.D.

;GET FORMAT TIME OUT VALUE
;GOTO LOCAL DISK HANDLER THEN
SIO

; IF NO ERRORS CONT FORMATING
;ELSE CK FOR DEVICE DONE ERROR
;N0, THEN ERROR EXIT

•ELSE CK FOR BAD SECTOR INFO
; RETURNED BY CONTROLLER

;BAD SECTORS RET ERR MSG

;NOT BAD SEC ERR, REQ ERR EXIT

JMP RETURN

;DO ERROR EXIT

(ZDRVA),Y

XFl

#0 ;SET

#2 ;TYPE = 2

(ZDRVA),Y

#$C3 ;SET MSN AND
(ZDRVA),Y ;NSA=107=2C3

(ZDRVA),Y

FORMAT

0E69 A902
0D6B 88
0D6C 9145
0E6E C8
0E6F C8
0E70 9145

3552
3553
3554
3555
3556
3557

LDA #$02

DEY

STA (ZDRVA),Y

INY

STA (ZDRVA),Y

ATARI DOS 2.0S

3558

;

0D7::

A00A

3559

LDY

#DVDSMP

0D74

A9FF

3560

LDA

#$FF

;SET SECTOR MAP TO

0D7f,

9145

3561

XF2

STA

(ZDRVA),y

;ALL ONES

0D7EI

3562

INY

0D7?i

C064

3563

CPY

#DVDSMP+90

0D7E1

D0F9

3564
3565

BNE

XF2

0D7D

A90F

3566

LDA

#50F

JDEALOCATE 1ST 4 SECTORS

0D7F

A00A

3567

LDY

fDVDSMP

;FOR BOOT

0D81

9145

3568
3569

STA

(ZDRVA),Y

0D8;i

A037

3570

LDY

#DVDSMP+45

; DEALLOCATE MIDDLE 9

0D8!.

A900

3571

LDA

0D8T

9145

3572

STA

(ZDRVA),Y

;FOR

0D8?'

3573

INY

jVTOC AND FILE DIR

0D8;i.

A97F

3574

LDA

#$7F

0D8C

9145

3575
3576

STA

(ZDRVA),Y

0D8e:

209510

3577
3578

JSR

WRTVTOC

•WRITE THE VTOC

0D9]

A900

3579

LDA

;0 FILLE DIR SECTORS

0D9;

3580

TAY

0D94

990114

3 581

XF3

STA

FILDIR.Y

;USE FILE DIR BUFFER

0D97

3582

INY

0D9f:

10FA

3583
3584

BPL

XF3

0D9;i

A907

3585

LDA

•WRITE TO ALL 8 DIR SECT

0D9C

8D0613

3586

STA

CDIRS

0091'

207110

3587

XF4

JSR

WRTDIR

0DA2

CE0613

3588

DEC

CDIRS

0DAE

10F8

3589
3590

;

BPL

XF4

0DA-

201912

3591
3592

;

JSR

DELDOS

•SET NO DOS

0DAA

4CEA12

3593

JMP

FGREAT

•DONE

LIST

DIRECTORY

0DA1D

3594

.PAGE "LIST DIRECTORY"

3595

3596

; LISTDIR -

■ LIST THE DIRECTORY

3597

; GDCHAR -

GET NEXT DIR CHARACTER

3598

: THE

DIRECTORY IS LISTED VIA OPEN

3599

; LIST

DIRECTORY FUNCTION EACH DIR

3600

; ENTRY THAT MATCHES THE FILE SPEC

3601

; IS CONVERTED TO A PRINTABLE FORMAT

3602

; INTO

A SECTOR BUFFER

THE GET BYTE

3603

; ENTRY IS

USED TO GET

THE PRINTABLE

3604

; CHARACTERS ONE AT A

TIME. THE

3605

; LAST

LINE PRINTED IS

ALWAYS A

3606

; COUNT OF

THE NUMBET

OF SECTORS IN USE

3607

; AND

THE NUMBER REMAINING AVAILABLE SECTORS

3608

;

3609

LISTDIR

0DA1)

A900

3610

LDA

0DA]?

8D0F13

3611

STA

TEMP4

0db:2

20210F

3612

JSR

SFDIR

.•SEARCH FOR A FILE NAME

0db:5

902C

3613

BCC

LDENTl

;BR IF FOUND

0DB7

B030

3614
3615
3616

GDCHAR

BCS

LDCNT

;BR IF NOT FOUND

0DB9

2C0F13

3617

BIT

TEMP4

;TEST FLAG

0DB<;

3053

3618
3619

BMI

LDDONE

;BR IF ALL DONE

0DB1?

AC0F13

3620

LDY

TEMP4

;GET COUNT OF CHARS SENT

0dc:l

B147

3621

LDA

(ZSBA),Y

;GET NEXT CHAR

ATARI DOS 2.0S

0DC3

8D0813

3622

STA

SVDBYT

; IN SVDBYT

BDce

EE0F13

3623

INC

TEMP4

;INC COUNT

0DC9

C99B

3624

CMP

#EOL

;TEST IF EOL DONE

0d<:b

D009

3625

BNE

GDCRTN

;BR NOT EOL

0DCD

C011

3626

CPY

#17

rWAS THIS AN ENTRY

0D(:f

B008

3627

BCS

LDENT

;BR IF IT WAS

0D131

A980

3628

LDA

#S80

;ELSE INDICATE END

0DD3

8D0F13

3629
3630

STA

TEMP4

;IN TEMP4

0DD6

4CF012

3631
3632

GDCRTN

JMP

GREAT

;DONE

0DD9

A900

3633

LDENT

LDA

r CLEAR CHAR COUNTER

0DDB

8D0F13

3634

STA

TEMP4

0DDE

20310F

3635

JSR

CSFDIR

r SEARCH FOR NEXT MA'

0D:51

B00e

3636
3637

LDENTl

BCS

LDCNT

;BR NO MORE MATCHES

0D33

20210E

3638

JSR

FDENT

; FORMAT ENTRY

0D136

4CF012

3639
3640

JMP

GREAT

;DONE

0D]39

208B10

3641

LDCNT

JSR

RDVTOC

;READ VTOC

0d:3c

A004

3642

LDY

♦DVDNSA+1

;GET # SECTOR AVR

00)! E

B145

3643

LDA

(ZDRVA),Y

0d:?0

3644

PHA

LIST DIRECTORY

0DP1 88
0DF2 B145
0DF4 A8
0DF5 68

0DF6 20570E

0DF9 A003
0DFB A20C
0DFD BD140E
0E00 9147
0E02 C8
0E03 CA
0E04 10F7
0E06 20670E

0E09 A900
0E0B 8D0F13
0E0E 4CEA12

0E11 4CF412

0E14 53

0E15 52

0E16 4F

0i;i7 54

0E;18 43

0e;19 45

0i;iA 53

0b:ib 20

0B:1C 45

0b;id 45

0E1E 52

0E1F 46

0e:20 20

000D

0i;2i
0i;21

3645

3646

3647

3648

3649 ;

3650

3651 ;

3652

3653

3654 MVFSCM

3655

3656

3657

3658

3659

3660 ;

3661

3662

3663

3664 ;

3665 LDDONE
3666

3667 ;

3668 FSCM

DEY

LDA (ZDRVA),Y

TAY

PLA

JSR CVDX

LDY #3

LDX #FSCML-1

LDA FSCM.X

STA (ZSBA),Y

INY

DEX

BPL MVFSCM

JSR CVDY

LDA #0

STA TEMP4

JMP PGREAT

jAND CONVERT

;SET EOL
rPUT IN CUTE
; MSG

SET CHAR CNT

JMP ERREOF ;END OF FILE
.BYTE "SROTCES EERF "

3669 FSCML = *-FSCM

35 .INCLUDE #E:

40 .INCLUDE #D:ATFMS3.

SRC

ATARI DOS 2.0S

LIST DIRECTORY

0E21

4000
4001
4002
4003
4004

0E2L

A000

4005

0E2 3

A920

4006

0E25

9147

4007

0E2 7

AE0513

4008

0E2i\

BD0114

4009

0E2D

2920

4010

0E2ir

F004

4011

0E31

A92A

4012

0E3:3

9147

4013

0E3!;

4014

0E3i5

A920

4015

0E3I3

9147

4016

0E3A

4017
4018

0E3I!

BD0614

4019

0E31i;

9147

4020

0E4I!I

4021

0E4;.

4022

0E4:>

C00D

4023

0E44

90F5

4024
4025

0E4(i

A920

4026

0E4(i

9147

4027

0E4A

4028

0E4H

8C0F13

4029
4030

0E4i;

AE0513

4031

0E5].

BC0214

4032

0E54

BD0314

4033
4034
4035

0E57

A264

4036

0E59

20710E

4037

0E5C;

A20A

4038

0E5i;

20710E

4039

0E6].

4040

0E6::

208D0E

4041
4042

0E6!i

A011

4043

0E67

A99B

4044

0E6S'

9147

4045

0E6Ei

A000

4046

0E6r>

8C0F13

4047

0E7e'

4048
4049

0E71

8E0E13

4050

.PAGE
; FORMAT DIR ENTRY INTO A SECTOR BUFFER
FDENT

LDY #0

LDA *$20

STA (ZSBA),Y

LDX CDIRD

LDA FILDIR+DFDFLl.X

AND #DFDLOC ;BUT IF FILE LOCKED

BEQ LDl

LDA # ' *

STA (ZSBA),Y

INY

LDA #$20

STA (ZSBA),Y

INY

; START AT DISPL ZERO
; START WITH A BLANK

; CHANGE TO AST

J FOLLOWED BY A BLANK

LD2

LDA FILDIR+DFDPPN,X ;MOVE THE 12 CHAR

STA (ZSBA),Y ;FILE NAME

I NX

INY

CPY #13

BCC LD2

LDA #S20

STA (ZSBA),Y

INY

STY TEMP4

.•FOLLOWED BY A BLANK
;SAVE INDEX =15

LDX CDIRD

LDY PILDIR+DFDCNT,X ;SET A,Y

LDA FILDIR+DFDCNT+1,X r=SECTOR COUNT

LDX #100

JSR CVDIGIT

LDX #10

JSR CVDIGIT

TYA

JSR STDIGIT

LDY #17

LDA #EOL

STA (ZSBA),Y

LDY #0

STY TEMP4
RTS

CVDIGIT STX TEMP3

CVDY

; CONVERT AND MOVE
;100S DIGIT

;10S DIGIT

;1S DIGIT

;THEN PUT OUT
;AND EOL

;SET CHAR CNT =

rSAVE DIGIT VALUE

LIST DIRECTORY

0E74 A2FF

4051
4052 ;

LDX

#SFF

0E76 8D0D13

4053 CVDl

STA

TEMP2

;SAVE CURR VALUE HI

0E79 8C0C13

4054

STY

TEMPI

?AND LOW

0E7C E8

4055

INX

; INC DIGIT COUNTER

0E7n 38

4056

SEC

JSUBRTACT DIGIT VAU

0E7E AD0C13

4057

LDA

TEMPI

;PROM CUR VALUE

0E81 ED0E13

4058

SBC

TEMP3

0E84 AS

4059

TAY

0E85 AD0D13

4060

LDA

TEMP2

0E88 E900

4061

SBC

ATARI DOS 2.0S

0E8A

B0EA

4062
4063

BCS

CVDl

0E8(:

4064

TXA

0E8I)

0930

4065

STDIGIT ORA

#?30

0E81?

AC0F13

4066

LDY

TEMP4

0E9:J

9147

4067

STA

(ZSBA),Y

0E94

EE0F13

4068

INC

TEMP4

0E97

AD0D13

4069

LDA

TEMP2

0E9A

AC0C13

4070

LDY

TEMPI

0E915

4071

RTS

;IF NOT GONE MINUS, DO AGAIN

; DIGIT TO ACU
;PLUS ASCII ZERO
;GET OUTPUT INDEX
;AND SET DIGIT
; INC OUTPUT INDEX
;LOAD VALUE HI
;AND VALUE LO

FILE NAME DECODE

0E9E

0E9E BD4403
0EA1 8543
0EA3 BD4503
0EA6 8544
0EAB A002
0EAh B143
88

3058
C93A
D0F7

0EAC
0EAD
0EAF
0EB1

0EB3 C8

0EB4 A20B
0EB6 A920

4072
4073
4074
4075
4076
4077
4078
4079
4080
4081
4082
4083
4084
4085
4086
4087
4088
4089
4090
4091
4092
4093
4094
4095
4096

4097
4098
4099
4100
4101
4102
4103
4104
4105
4106
4107
4108
4109
4110
4111
4112

.PAGE "FILE NAME DECODE"

FNDCODE - DECODE A FILE NAME

THE USER FILENAME IS POINTED TO BY
ZBUFP, IT IS ON THE FORM P.X WHERE P
IS THE PRIMARY FILE NAME (1 TO 8 CHARS)
AND X IS THE EXTENDED FILE NAME
(0 TO 4 CHARS). THE PERIOD IS OPTIONAL
(IF NOT PRESENT, THEN NO EXTENSION).
THE DECODED FILENAME WILL BE 12 CHARS
IN LENGTH. THE P FIELD WILL BE
LEFT JUSTIFIED IN THE 1ST 8 BYTES.
THE X FIELD WILL BE LEFT JUSTIFIED IN
THE LAST 4 BYTES. BLANKS ARE USED
TO PAD THE FIELDS TO FULL SIZE.
IF THE USER SPECIFIED P OR X FILEDS
CONTAIN MORE THAN 8 OR 4 CHARS, THEN THE
EXTRA CHARS ARE IGNORED. THE '*'
WILD CARD CHAR WILL CAUSE THE REST
OF THE FIELDS TO FILLED WITH THE
'?■ WILD CARD CHAR. ANY NON-ALPHANUMERIC
CHAR TERMINATES THE FILENAME.

FNDCODE

FD0A

FD0B

FNDCNX

LDA

ICBAL,X

STA

ZBUFP

LDA

ICBAH,X

STA

ZBUFP+1

LDY

;FIND THE

LDA

( ZBUFP ),Y

DEY

BMI

FNDERR

;BR IF 25

CMP

#' :

BNE

FD0A

■D'

LDX

LDA

#11
*$20

0EB8 9D5913 4113 FD0

4114

4115

4116 ;

0EBE A200 4117

0EC0 8E0C13 4118

4119 ;

4120 ;

4121 FDl
4122

0EBB CA
0EBC 10FA

0EC3 C8
0EC4 B143

STA FNAME,X

DEX

BPL FD0

LDX #0

STX EXTSW

r CLEAR FILENAME TO BLANKS

;SET FNAME CHAR CNT TO
;SET NOT IN EXTENSION

INY

LDA

;INC ZBUFP INDEX
(ZBUFP), Y rGET BUF CHAR

ATARI DOS 2.0S

FILE NAME DECODE

4123

;

0EC6

C92A

4124

CMP

#'* •

0EC8

D00B

4125
4126

;

BNE

Fr3 ;

0ECA

A93F

4127

FD2

LDA

#'? ;

0ECC

200A0F

4128

JSR

FDSCHAR ;

0ECF

90F9

4129

BCC

FD2 ;

0ED1

10F0

4130

BPL

FDl ;

0ED3

302E

4131
4132

BMI

FDEND ;

0ED5

C92E

4133

FD3

CMP

#•• :

0ED7

D00C

4134

BNE

FD4 ;

0ED9

2C0C13

4135

BIT

EXTSW

0EDC

3025

4136

BMI

FDEND ;

0EDE

A208

4137

LDX

#8 ;

0EE0

6E0C13

4138

ROR

EXTSW

0EE3

90DE

4139
4140

BCC

FDl ;

0EE5

C93F

4141

FD4

CMP

#'? W

0EE7

F014

4142
4143

BEQ

FD6 ;

0EE9

C941

4144

CMP

#'A ;

0EEB

9004

4145

BCC

FD5

0EED

C95B

4146

CMP

#$5B ;

0EEF

900C

4147
4148

;

BCC

FD6 ;

0EF1

E000

4149

FD5

CPX

0EF3

F012

4150
4151

;

BEQ

FNDERR

0EF5

C930

4152

CMP

#$30

0EF7

900A

4153

BCC

FDEND

0EF9

C93A

4154

CMP

#$3A ;

0EFB

B006

4155
4156

BCS

FDEND ;

0EFD

200A0F

4157

FD6

JSR

FDSCHAR r

0F00

4CC30E

4158
4159

JMP

FDl :

0F03

AE0113

4160

FDEND

LDX

CURFCB ;

0F06

4161
4162

RTS

0F07

4CC512

4163

FNDERR

JMP

ERRFN

TEST FOR WILD CARDS
BR NOT WILD CARD

LOAD 7 WILD CARD

GO STORE IT

BR IF PORX NOT FULL

BR IF AT START OF X
BR IF AT X END

WAS CHAR FIELD SEPERATOR

BR IF NOT

WAS THERE ALREADY 1 CHAR

BR IF WAS END

ADV FNAME INDEX TO XFIELD

SET EXTSW - MINUS

CONT WITH NEXT CHAR

WAS IT WILD CARD
BR IF WILD CARD

IS CHAR ALPHA
BR NOT ALPHA
TEXT HI ALPHA
BR IF NOT APLHA

IF FIRST CHAR NOT
ALPHA THEN ERROR

IS CHAR NUMERIC
BR NOT NUMERIC (END OF NAME)
TEST NUMERIC HI
BR NO NUMBER

STORE THE CHAR

AND CONTINUE WITH NEXT

RESTORE X REG

INDICATE FILENAME ERROR

FMS - 128/256 BYTE SECTOR (2.0S)
FILE NAME DECODE

0F0A

4164

.PAGE

4165

4166

; FDSCHAR -

STORE FILENAME CHAR

4167

4168

; ON ENTRY

4169

; A = CHAR

4170

; X = NEXT

FN POSITION

4171

4172

; ON EXIT

4173

; CARRY - SET IF FIELD FULL

4174

; MINUS - IF START OF EXECUTION

4175

; PLUS - IF END OF EXECUTION

4176

;

4177

FDSCHAR

0F0A

E008

4178

CPX

#8 ;AT EXECUTION

0F0C

900D

4179

BCC

FDSC2 ;BR IF NOT

0F0E

F005

4180
4181

BEO

FDSCl ;BR IF 1ST

CHAR OF

0F10

E00C

4182

CPX

#12 ;AT END OF

EXIT

0F12

9007

4183

BCC

FDSC2 ;BR NOT AT

END

ATARI DOS 2.0S

0F14 60

4184
4185 (

RTS

0F15 2C0C13

4186 FDSCl

BIT

EXTSW

0F18 3001

4187

BMI

FDSC2

0F1A 60

4188
4189 ;

RTS

0F1B 9D5913

4190 FDSC2

STA

FNAME.X

0F1E E8

4191

INX

0F1F 18

4192

CLC

0F20 60

4193

RTS

;DO NOT STORE CHAR UNLESS
; PERIOD WAS SEEN

;SET CHAR INTO NAME
;INC TO NEXT CHAR

DIRECTORY SEARCH

0F21

4194

.PAGE "DIRECTORY SEARCH"

4195 ,

4196 ;

SFDIR - SEARCH FILE

DIRECTORY

4197

CSFDIR - FILE DIRECTORY SEARCH

4198

4199

THE

FILE DIRECTORY

IS SEARCHED FOR THE

4200

FILENAME IN FNAME .

THE SEARCH STARTS

4201

AT THE CENTRAL SECTOR+1 AND WILL CONTINUE

4202

FOR

UP TO

A TOTAL OF 8 SECTORS. WHEN

4203

TESTING FOR FNAME MATCH, '7' FNAME

4204

CHARS WILL ALWAYS MATCH THE CORESPONDING

4205

DIR

FILENAME CHAR.

IF A MATCH IS FOUND

4206

CDIRS CONTAINS THE

RELATIVE DIRECTORY SECTOR

4207

NUMBER (0

-7) AND CDIRD (AND THE Y REG)

4208

CONTAINS THE DISPLACEMENT OF THE ENTRY.

4209

AFTER A MATCH HAS BEEN FOUND, THE DIRECTORY CAN

4210

BE SEARCHED FOR ANOTHER MATCH VIA THE CSFDIR

4211

ENTRY POINT. IF A

MATCH HAS NOT BEEN FOUND

4212

THEN DHOLES AND DHOLED WILL POINT TO A

4213

DIRECTORY

HOLE THAT

CAN BE USED.

4214

• IF DHOLED

= FF THEN THE DIRECTORY IS FULL.

4215

THE

CARRY

IS RETURNED CLEAR IF FILE FOUND,

4216

SET

IF FILE NOT FOUND.

4217

4218

3FDIR

0F21

A9FF

4219

LDA

#$FF

;INIT TO -1

0F23

8D0213

4220

STA

DHOLES

;DIR HOLE SECTOR

0F26

8D0613

4221

STA

CDIRS

;CUR DIR SECTOR

0F29

8D0713

4222

STA

SFNUM

;FILE NUMBER

0F2C

A970

4223

LDA

#570

;INIT TO -16 (-ENTRY LENGTH)

0E2E

8D0513

4224
4225

•

STA

CDIRD

;CUR DIR DISPL

4226

::sFDiR

0F31

EE0713

4227

INC

SFNUM

0F34

4228

CLC

0F35

AD0513

4229

LDA

CDIRD

;CDIRD=CDIRD+ENTRY LEN

0S38

6910

4230

ADC

#DFDELN

0B3A

1011

4231

BPL

SFD2

;IF RESULT <128 THEN BR

4232

; ELSE AT END OF DIR

SECT

0F3C

EE0613

4233

INC

CDIRS

,-INC TO NEXT DIR SECTOR

0F3F

A908

4234

LDA

;TEST END OF DIR

0F41

CD0613

4235

CMP

CDIRS

0F44

9002

4236

BCC

SPDl

;BR NOT END

0F46

F048

4237
4238

BEQ

SDRTN

0F48

206E10

4239

3FD1

JSR

RDDIR

;READ THE NEXT DIR RECORD

0S'4B

A900

4240
4241

LDA

;SET DIR DISPL =

0I'4D

8D0513

4242

SFD2

STA

CDIRD

;SET NEW DIR DISPL

0F50

4243
4244

TAY

;PUT DISPL IN Y AS INDEX

ATARI DOS 2.0S

DIRECTORY SEARCH

0F5;.
0F54

0F5<i
0F5B
0F5/1

B90114
F01D

301B
2901
D0D5

0F5C
0F5i:
0F6]
0F6;i

0F6;;

0F6£:

0F6;i.

0F6E.
0F6C
0F6F

0F7ei

0F73

0F73
0F7fi

0F761
0F7E:
0F7E;
0F81
0F84
0F87

0F8f.
0F8ri

A200

BD5913

C93F

F005

D90614

D0C7

E00B

D0EE

18
901D

AD0213
1012

AD0613
8D0213
AD0513
8D0313
AD0713
8D0413

B90114
30A2

0F8F 38

0F90
0F93

AE0113
60

4245
4246

4247
4248
4249
4250
4251
4252
4253
4254
4255
4256

4257
4258
4259
4260
4261
4262
4263
4264
4265
4266
4267
4268
4269
4270
4271
4272
4273
4274
4275
4276
4277
4278
4279
4280
4281
4282
4283
4284

4285
4286

LDA FILDIR+DFDFLl.Y :GET FLAG 1

BEQ SFDSH ;BR IF UNUSED (END OF USED

ENTRIES)
BMI SFDSH ;BR IF DELETED
AND #DFDOUT ;IF OPEN OUTPUT
BNE CSFDIR ;DON'T FIND IT

ENTRY IN USE, TEST FOR MATCH

SFD3

SFD4

LDX
LDA
CMP
BEQ

CMP

BNE
INX
INY
CPX
BNE

CLC
BCC

LDA
BPL

#0 ;TEST MATCH ON 12 CHARS
FNAME.X ;FILE NAME CHAR
#'7 ;IS FNC WILD CARD
SFD4 ;THEN IT MATCHES
FILDIR+DFDPFN.Y ;ELSE IT MUST MATCH FOR

REAC
CSFDIR ;IF NOT MATCH THEN TRY NEXT
;INC CHAR CNT

; ELSE

LDA
STA
LDA
STA
LDA
STA

SFDSHl LDA
BMI

#11
SFD3

SDRTN

DHOLES
SFDSHl

CDIRS

DHOLES

CDIRD

DHOLE D

SFNUM

DHFNUM

;TEST ALL

rAND CONTINUE CHECK

;WE HAVE A MATCH

rIF DHOLES NOT MINUS

;THEN ALREADY HAVE A GOOD HOLE

;MOVE CURR DISPL SECTOR
;AND CURRENT DIR DISPL
;T0 HOLE SECTOR AND DISPL

;SAVE HOLE
;FILE NUMBER

FILDIR+DFDFLl.Y ;IF HOLE WAS A DELETED
CSFDIR : ENTRY THEN CONTINUE

ELSE WE ARE AT END OF

SDRTN LDX CURFCB
RTS

;USED ENTRIES THUS FILE NOT

FOUND
: RESTORE X REG

WRITE DATA SECTOR

0F94

0F94
0F97

0F99
0F9A

0F9C
0F9E
0FAe
0FA3
0FA5

BD8513
300F

0A
1009

9D8513

20F80F

3024

4C0F10

4287
4288
4289
4290
4291
4292
4293
4294
4295
4296
4297
4298
4299
4300
4301
4302
4303

.PAGE "WRITE DATA SECTOR"
; WRTNXS - WRITE NEXT SECTOR
WRTNXS

LDA FCBFLG.X
BMI WRTNl

ASL
BPL

ASL
STA
JSR
BMI
WRUl JMP

A
WRUl

FCBFLG.X

WRCSIO

WRNERR

RDNXTS

;IF ACQUIRING SECTORS
fTHEN NOT UPDATE

;IF SECTOR NOT MODIFIED
;THEN DON'T IT

.•TURN OFF FLAG BITS
rWRITE CURRENT SECTOR
.•BR IF BAD I/O
;ELSE READ NEXT SECTOR

ATARI DOS 2.0S

0FAB

2006H

4304
4305

WRTNl

JSR

GETSECTOR

•GET A NEW SECTOR

0FAH

BD8713

4306

WRTLSEC LDA

FCBDLN.X

•GET DATA LEN

0FAIi;

ACFB12

4307

WRTLSl

LDY

DRVLBT

•INTO LAST BYTE

0fb:l

9147

4308
4309

STA

(ZSBA),Y

•OF SECTOR

0FB;i

BD8C13

4310

WRTN2

LDA

FCBLSN+1 , X

;MOVE LINK SECTOR

0FB(J

1D8113

4311

ORA

FCBFNO.X

•PLUS FILE NUM

0FB9

ACF812

4312

LDY

DRVMDL

•TO BYTES 126,127

0FB(:

9147

4313

STA

(ZSBA),Y

;0F SECTOR BUFF

0FB1S

4314

INY

0FB1?

BD8B13

4315

LDA

FCBLSN.X

0FC:2

9147

4316
4317

STA

(ZSBA),Y

0FC4

20F80F

4318

JSR

WRCSIO

.•WRITE SECTOR

0FC7

1011

4319
4320

BPL

WRTN5

;BR NOT ERROR

0FC')

AD0303

4321

WRNERR

LDA

DCBSTA

rSAVE ERROR STATUS

0FC<:

8D0F13

4322

STA

TEMP4

0FC1?

A900

4323

LDA

; CLOSE FILE

0FDL

9D8213

4324

STA

FCBOTCX

0FD4

AD0F13

4325

LDA

TEMP4

; RECOVER ERROR CODE

0FD7

4CD312

4326
4327
4328

!
WRTN5

JMP

RETURN

0FD,\

FE8F13

4329

INC

FCBCNT.X

:INC SECTOR CNT

0fd:3

D003

4330

BNE

WRTN6

0fd:?

FE9013

4331
4332

WRTN6

INC

FCBCNT+1 , X

0FE2

200210

4333

JSR

MVLSN

;LINK TO CUR

0FE5

A900

4334

LDA

0FE7

9D8B13

4335

STA

FCBLSN.X

;LINK =

0FEA

9D8C13

4336

STA

FCBLSN+1, X

0FED

9D8713

4337

STA

FCBDLN.X

;DLN =

WRITE DATA SECTOR

0FFI3

ADF812

4338

LDA

DRVMDL

0FF3

9D8613

4339
4340

WRNRTS

STA

FCBMLN.X

0FF5

4341

CLC

0FF7

4342
4343

;

RTS

0FF3

4344

WRCSIO

SEC

;WRITE CUR

0FF9

BD8A13

4345

RWCSIO

LDA

FCBCSN+1,X

0ff:

BC8913

4346

LDY

FCBCSN.X

0FFF

4CF711

4347
4348

JMP

DSIO

1002

BDSBIS

4349

MVLSN

LDA

FCBLSN.X rMOVE LINK

1005

9D8913

4350

STA

FCBCSN.X

100B

BD8C13

4351

LDA

FCBLSN+1, X

100B

9D8A13

4352

STA

FCBCSN+1,X

100E

4353
4354

RTS

100F

.INCLUDE #E:

100F

.INCLUDE #D:ATFMS4.SRC

RE*.D DATA SECTOR

.PAGE "READ DATA SECTOR"
RDNXTS - READ NEXT SECTOR

10eiF 5000
5001
5002

5003 ;

5004 RDNXTS

10flF BD8513 5005 LDA FCBFLG.X .-IF NOT UP0 MODE
1012 F003 5006 BEQ RDNSO ;BR

ATARI DOS 2.0S

1014

4C940F

5007

JMP

WRTNXS

.-ELSE WRITE FIRST

1017

5008

RDNSO

1017

BD8B13

5009

LDA

FCBLSN,X

;IF LSN NOT

101A

1D8C13

5010

ORA

FCBLSN+1,X

,- ZERO

101D

D002

5011

BNE

RDNSl

;BR

101F

5012

SEC

;ELSE EOF

1020

5013

RTS

1021

200210

5014

RDNSl

JSR

MVLSN

rMOVE LINK TO CURRENT

1024

5015

CLC

;READ

1025

20F90F

5016

JSR

RWCSIO

; CURRENT SECTOR

1028

3035

5017
5018

BMI

RDIOER

,-BR IF OK READ

5019

; ELSE

GOTO

I/O ERROR

5020

102A

ACF812

5021

LDY

DRVMDL

102D

B147

5022

LDA

(ZSBA) ,Y

,-TEST FOR SAME

102F

29FC

5023

AND

*$FC

rFILE NO

1031

DD8113

5024

CMP

FCBFNO.X

1034

D02C

5025
5026

BNE

RDFNMM

;IF NOT THEN ERROR

1036

B147

5027

LDA

(ZSBA) ,Y

;MOVE LINK SECTOR

1038

2903

5028

AND

#$03

103A

9D8C13

5029

STA

FCBLSN+1,X

103D

5030

I NY

103E

B147

5031

LDA

(ZSBA),Y

1040

9D8B13

5032
5033

STA

FCBLSN,X

1043

5034

I NY

;INC TO LEN BYTE

1044

B147

5035

LDA

(ZSBA) ,Y

;GET LEN BYTE

1046

5036

PHA

;SAVE IT

1047

BD8413

5037

LDA

FCBSLT.X

;GET SECTOR LEN TYPE

104A

D008

5038
5039

BNE

RDNS3

;BR IF NEW TYPE

104C

5040

PLA

rGET LEN

104D

3002

5041

BMI

RDNS2

;BR IF OLD SHORT SECTOR

104F

A97D

5042

LDA

#125

;ELSE SET FULL SECTOR

1051

297F

5043

RDNS2

AND

#S7F

jTURN OFF MSB

1053

5044
5045

PHA

; BALANCE STACK

1054

5046

RONS 3

PLA

1055

9D8613

5047
5048

STA

FCBMLN.X

;SET MAX LEN

1058

A900

5049

LDA

;SET CUR DATA LEN =

105A

9D8713

5050

STA

FCBDLN.X

READ DATA SECTOR

105D

5051

CLC

105E

5052

RTS

105F

20E512

5053

RDIOER

JSR

ERRIO

;I/0 ERROR

1062

5054

RDFNMM

jFILE mjMBER MISMATCH

1062

BD4203

5055

LDA

ICCOM.X

1065

C921

5056

CMP

#$21

rWAS THIS DELETE

1067

F003

5057

BEQ

RDDELE

;BR IF DELETE

1069

20C712

5058

JSR

ERFNMM

;BR NOT DELETE

106C

5059

RDDELE

SEC

; INDICATE EOF TO DELETE

106D

5060
5061

RTS

READ/WRITE DIR

106E

106E 18

5062
5063
5064
5065
5066 RDDIR CLC

.PAGE "READ/WRITE DIR"
RDDIR/WRDIR READ/WRITE DIRECTORY
;SET READ

ATARI DOS 2.0S

i0e.F

9001

5067
5068

BCC

DIRIO

1071

5069
5070

WRTDIR

SEC

SET WRITE

1072

5071

DIRIO

PHP

SAVE READ WRITE

107 3

A914

5072

LDA

#FILDIR/256 rMOVE BUF ADDR

1075

8D0503

5073

STA

DCBBUF+1 ,

TO DCB

1078

A901

5074

LDA

#FILDIRJ.255

107A

8D0403

5075
5076

STA

dcb6uf

107D

5077

CLC

10-E

AD0613

5078

LDA

CD IRS

CDIRS+

10fil

6969

5079

ADC

#S69

((40*18)/2)+l

10f!3

5080

TAY

INTO A,Y

10EI4

A901

5081

LDA

IS DIR SECTOR NUMBER

10EI6

6900

5082
5083

ADC

10(18

4CAB10

5084
5085

;

JMP

DSYSIO

GO DO SYSTEM I/O

READ/WRITE

VTOC

10HB

5086

.PAGE "READ/WRI

rE VTOC"

5087

5088

; RDVTOC/WRCTOC - READ/WRITE VTOC

5089

;

5090

RDVTOC

108B

A005

5091

LDY

♦DVDWRQ

•IF WRITE REQD

108D

B145

5092

LDA

(ZDRVA),Y

10«F

F001

5093

BEQ

RDVGO

1091

5094

RTS

10<»2

5095

RDVGO

CLC

;SET READ

1093

9007

5096
5097

BCC

VTIO

5098

WRTVTOC

1095

A005

5099

WRVTOC

LDY

♦ DVDWRQ

■TURN OFF

1097

A900

5100

LDA

•WRITE READ

1099

9145

5101

STA

(ZDRVA),Y

109B

5102
5103
5104

;

SEC

109C

5105

VTIO

PHP

•SAVE R/W

109D

A546

5106

LDA

ZDRVA+1

■MOVE BUF ADDR

10?IF

8D0503

5107

STA

DCBBUF+1

•TO DCB

10;i2

A545

5108

LDA

ZDRVA

10;i4

8D0403

5109
5110

;

STA

DCBBUF

10^1 7

A068

5111

LDY

#S68

•READ SECTOR

10;i9

A901

5112
5113
5114

DSYSIO

LDA

• (40*18)/2

i0;iB

5115
5116

DSYSIA

PLP

i0;,c

AEFE12

5117

LDX

DRVTYP

•LOAD DRIVE TYPE

i0;iF

206C07

5118

JSR

BSIO

■GO DO I/O

10112

3001

5119

BMI

DSIOER

•BR IF ERROR

10E14

5120
5121
5122

;

RTS

RETURN

10E15

C983

5123

DSIOER

CMP

#DCBDER

WAS IT DATA ERROR

10BI7

F003

5124

BEQ

DEAD

BR IF WAS

10E19

4CE512

5125
5126

JMP

ERRIO

ELSE USER PROBLEM

10E1C

4CC912

5127
5128
5129
5130

DEAD

;

; OPEN

JMP
VTOC

ERRSYS

FATAL ERROR

ATARI DOS 2.0S

5131 OPVTOC

10B:F 208B10 5132

10C2 4C9510 5133

5134

5135

5136

JSR
JMP

RDVTOC
WRTVTOC

;READ IT
;THEN WRITE IT

INSURES NOT PROTECTED

PREK SECTOR
10C!>

10C!>
10C»
10CH
10C1)
10C1'
10D:.
10D4
10D-'
10D()
10D9

BD8913

1D8A13

F038

A900

A003

5E8A13

7E8913

D0F6

10DEI A005

10DI> eA

10Di; 88

10Dr D0FC

10E]. A8

10e;! A900

10E4 38

10E!; GA

10E(; 88

10EV 10FC

10E9 48

10E?. BD8913

10EII 690A

10EI' A8

10Fei 68

10F] 1145

10f;: 9145

10F5
10F7
10FSI
10F/.
10FC:
10FI
10FF
1101
1103

110!
110!

A003

B145

6901

9145

B145

6900

9145

5137
5138
5139
5140
5141
5142
5143
5144
5145
5146
5147
5148
5149
5150
5151
5152
5153
5154
5155
5156
5157
5158
5159
5160
5161
5162
5163
5164
5165
5166
5167
5168
5169
5170
5171
5172
5173
5174
5175
5176
5177
5178
5179
5180
5181
5182
5183
5184
5185

.PAGE "FREE SECTOR"

;

; FRESECT - FREE CURRENT SECTOR

FRESECT

FSl

FS2

FS3

LDA

FCBCSN.X

ORA

FCBCSN+1,X

BEQ

FSRTS

LDA

LDY

LSR

FCBCSN+1,X

ROR

FCBCSN.X

ROR

DEY

BNE

FSl

LDY

ROR

DEY

BNE

FS2

TAY

LDA

SEC

ROR

DEY

BPL

FS3

PHA

LDA

FCBCSN.X 1

ADC

fDVDSMP i

TAY

PLA

ORA

(ZDRVA),Y ■

STA

(ZDRVA).Y ;

LDY

#DVDNSA :

LDA

(ZDRVA).Y

CLC

ADC

STA

(ZDRVA) .Y

INY

LDA

(ZDRVA),Y

ADC

STA

( ZDRVA ) , Y

; DIVIDE SECTOR #

;BY 3 TO GET BYTE NO
rWITH REM IN ACU

TO FOR BYT BIT NO

■BIT NO (0-7) INTO Y

SHIFT IN A BIT

TO PROPER LOCATION

rSAVE MASK

GET BYTE NO

ADD OFFSET TO SMAP
■RESULT IS VTOC INDEX

GET BIT MASK

OF BIT TO BIT MAP

AND SET RESULTS

INC NO OF SECTORS AVAIL

FSRTS

GET SECTOR
11106

.PAGE "GET SECTOR"

5186

5187 ;

5188 ; GET SECTOR - GET A FREE SECTOR FOR

5189 ; USE IN FCB AT X REG. THE SECTOR

5190 jNUMBER IS PLACED IN FCBLSN

ATARI DOS 2.0S

net Aei09

110fl C8
110?i C064
110B B054
110D B145
110F F0F7

1111
1114
lli;i
llKi
lllH
lllA

iiic;
mi:

lllF

112:.
ii2;t

8C0C13

A003

B145

E901

9145

B145

E900

9145

1121; C8
112r) A9FF
1120 9145

112A 68
112H A0FF

1121) C8
1121! 0A
1121' 90FC
1131 8C0D13
1134 4A
88
10FC
11313 AC0C13
11313 9145

11315
11315

5191
5192
5193
5194
5195
5196
5197
5198
5199
5200
5201
5202
5203
5204
5205
5206
5207
5208
5209
5210
5211
5212
5213
5214
5215
5216
5217
5218
5219
5220
5221
5222
5223
5224
5225
5226
5227
5228
5229
5230
5231
5232
5233
5234
5235
5236

THE SEARCH FOR A FREE SECTOR STARTS
AT THE DVDSMP BYTE. SECTORS ARE
NUMBERED SEQUENTIALLY FROM ZERO TO
MAXSM WITH THE LEFT BIT OF THE DVDSMP
BEING WITH ZERO.

GETSECTOR
LDY

GSl

GS3

#DVDSMP-1 ;SET Y TO START MAP-1

I NY ;INC SMAP INDEX

CPY ♦90+DVDSMP ;AT END OF MAP?

BCS GSERR ;BR IF AT END

LDA (ZDRVA),Y ; GET A MAP BYTE

BEQ GSl ;BR NO FREE SECTOR IN BYTE

;SAVE MAP INDEX

;DEC NO OF SECTORS AVAIL

STY

TEMPI

PHA

SEC

LDY

#DVDNSA

LDA

(ZDRVA),

SBC

STA

(ZDRVA) ,

INY

LDA

( ZDRVA ) ,

SBC

STA

(ZDRVA) ,

INY

LDA

#$FF

STA

(ZDRVA),

PLA

LDY

#$FF

INY

ASL

BCC

GS2

STY

TEMP 2

LSR

DEY

BPL

GS3

LDY

TEMPI

;SET READ REQD

;SET BIT COUNTER =-1

; SHIFT MAP BYTE

; UNTIL A FREE SECTOR

; FOUND

;SAVE BIT NUMBER

;AND SHIFT BYTE

; BACKS TO ITS ORIGINAL

; POSITION AND PUT IT

rBACK INTO THE MAP

STA ( ZDRVA ),Y

GET SECTOR

113D 38
1131: AD0C13
1141. E90A

1143 A000
114!i 8C0C13

1148 0A

1149 2E0C13
114(: C8
1141) C003
114F 90F7

115:. 18
1152 6D0D13
115,'j 9D8B13
1158 AD0C13
115B 6900

5237

5238

5239

5240 ,-

5241

5242

5243 ;

5244 GS4
5245
5246
5247
5248
5249 r
5250
5251
5252
5253
5254

SEC

LDA TEMPI

SBC #DVDSMP

LDY #0

STY TEMPI

A
TEMPI

ASL
ROL
INY

CPY #3
BCC GS4

CLC

ADC TEMP2

STA FCBLSN,

LDA TEMPI

ADC #0

r SECTOR NAP BYTE
;=DISPL-DVDSMP

; CLEAR SECT NO HI
rMULT REL SECTOR MAP

,-ADD BIT NO TO
; SECTOR #
;AND PUT INTO
; FCBLSN

ATARI DOS 2.0S

11;;d 9D8C13 5255

5256 ;

1160 60 5257

5258 ;

1161 4CCB12 5259 GSERR JMP ERRNSA

5260 ;

STA FCBLSN+1 , X
RTS

;N0 SECTOR AVAIL

SETUP ROUTINE

1164

1164 A99F
1166 8549
1168 8E0113

116B BA
11 6C E8
Hi5D E8
116E 8E0013

1171 AE0113
1174 A421
1176 8C0103
1179 88
117A B92913
117D 8545
117F B93113
1182 8546

1184 B91113
1187 F052
1189 8DFE12

118C A8
118D B9F812
11 '90 8DF812
ll'>3 B9FB12
1196 8DFB12

1199 BC8813
119C 88
119D 1031

119F A000
llAl B91913
11A4 F008
11A6 C8
11A7 C010
11A9 90F6

llAB 4CCD12

llAE ADFE12
llBl 4A
11B2 B010

5261
5262
5263
5264
5265
5266
5267
5268
5269
5270
5271
5272
5273
5274
5275
5276
5277
5278
5279
5280
5281
5282
5283
5284
5285
5286
5287
5288
5289
5290
5291
5292
5293
5294
5295
5296
5297
5298
5299
5300
5301
5302
5303
5304
5305
5306
5307
5308
5309
5310
5311

.PAGE "SETUP ROUTINE"

SETUP - A ROUTINE USED FOR ALL COMMANDS
TO SET UP FMS CONTROLL CELLS
TO ACCESS A PARTICULAR FILE.

LDA #$9F
STA ERRNO
STX CURFCB

TSX
INX
I NX
STX ENTSTK

LDX
LDY
STY
DEY
LDA
STA
LDA
STA

LDA
BEQ
STA

GSBl
GSB2

GSB3
GSB4

LDY
LDA
BEG
INY
CPY
BCC

CURFCB
ICDNOZ
DCBDRV

DBUFAL.Y
ZDRVA
DBUFAH,Y
ZDRVA+1

DRVTBL.Y

DERRl

DRVTYP

TAY

LDA DRVMDL.Y

STA DRVMDL

LDA DRVLBT.Y

STA DRVLBT

LDY FCBBUF.X

DEY

BPL SSBA

SECTBL.Y

GSB4

#16
GSBl

JMP ERRNSB

LDA DRVTYP

LSR A

BCS GSB5

;INIT ERROR CODE
rTO ZERO
rSAVE FCB

;GET CURRENT FCB

;MOVE DRIVE NO

rTO DCB

;DEC FOR ACCESS TO TABLES

;MOVE WRITE BUFFER

;ADD TO ZERO PAGE PTR

;GET DRIVE TYPE
;BR IF NOT EXISTS
rSAVE TYPE

jMOVE MAX DATA LEN
;AND LAST SECTOR BYTE
;DISPL TO LAST OF
; TABLES

;GET SECTOR BUF *

;DEC TO ACCESS TBL

;BR IF ONE IS ALLOCATED

;IF NON ALLOCATED
;TRY TO FIND ONE
;BR ONE FOUND
;DEC TRY COUNT

;BR MORE TO TRY

;N0 SECTOR BUFFERS AVAIL

; FOUND ONE IF 256 BYTES
.•DRIVE NEEDED TO CONT
;BR NOT 256 BYTES

SETUP ROUTINE

11:34 C8

5312

INY

1135 C010

5313

CPY

#16

1137 B0F2

5314

BCS

GSB3

1139 B91913

5315

LDA

SECTBL.Y

;ELSE TRY NEXT CONTIG
;TEST END OF BUFFERS
:AND BR IF NO MORE
;ELSE SEE IF ITS THREE

ATARI DOS 2.0S

IIBC D0E8
IIBEI 88

IIBF A980
llCl 991A13

11C4 A980
llC«i 991913
11C9 98
IICA 9D8813
IICI) FE8813

IIDH B93913
1103 8547
llDIi B94913
11D8 8548

IIDA 60
11D13 4CCF12

5316
5317
5318 ;
5319
5320

5321 ;

5322 GSB5
5323
5324
5325
5326

5327 ;

5328 SSBA
5329
5330
5331

5332 ;

5333 ;
5334

5335 7

5336 DERRl

BNE GSB2
DEY

;BR NOT FREE

LDA #S80 ; ALLOCATE SECOND OF 2

STA SECTBL+l,y

LDA #$80 ; ALLOCATE FIRST OR ONLY

STA SECTBL.Y

TYA

STA FCBBUF,X ;POT BUF NO INTO FCB

INC FCBBUF.X ;INC BUF NO SO NOT ZERO

LDA SABUFL.y ;MOVE BUFFER ADDR

STA ZSBA ;T0 ZERO PAGE PTR

LDA SABUFH.Y

STA ZSBA+1

RTS

JMP ERRDNO ;BAD DRIVE NO

SETUP ROUTINE

11D15

5337

.PAGE

5338

;

5339

; FREE

SECTOR BUFFERS

5340

;

IIDE

5341

FRESBUF =

IIDE

BC8813

5342

LDY

FCBBUF.X

■GET BUF NO

llEl

F013

5343

BEO

FSBR

•BR IF NONE

11E3

5344

DEY

;DEC FOR TBL ACCESS

11E4

A900

5345

LDA

•FREE

11E6

9D8813

5346

STA

FCBBUF , X

;IN FCB

11E9

991913

5347

STA

SECTBL.Y

;AND TABLE

llEC

ADFE12

5348

LDA

DRVTYP

;IF 128 BYTES

llEF

5349

LSR

; DRIVE

11F0

B004

5350

BCS

FSBR

;FREE ONLY ONE

11F2

5351

LSR

;ELSE

11F3

991A13

5352

STA

SECTBL+1,Y

;FREE 2

11F6

5353
5354

FSBR

;

RTS

DATA SECTOR I/O

11F7

5355

.PAGE "DATA SI

:cn

^OR I/O"

5356

5357

; DSIO

- DATA SECTOR

I/O

5358

5359

DSIO

11F7

5360

PHA

SAVE ACU DATA

11F8

A547

5361

LDA

ZSBA

WRITE SECTOR BUF

UFA

8D0403

5362

STA

DCBBUF

ADR MOVED TO

IIFD

A548

5363

LDA

ZSBA+1

DCB

IIFF

8D0503

5364

STA

DCBBUF+1

1202

5365
5366

PLA

r RESTORE ACU

1263

AEFE12

5367

LDX

DRVTYP

1286

206C07

5368

JSR

BSIO

;D0 THE l/O

1229

5369
5370

;

RTS

WRITE DOS

120A

5371

.PAGE "WRITE

DOS"

5372

;

ATARI DOS 2.0S

5373

; WRTDOS -

WRITE DOS

TO DISK

5374

;

5375

WRTDOS

120A

BC8913

5376

LDY

FCBCSN.X

;MOVE START ADDR

120D

BD8A13

5377

LDA

FCBCSN+1 ,

1210

205312

5378

JSR

SETDSO

rWRITE SECTOR

1213

206712

5379

JSR

WD0

; WRITE DOS

1216

4CF012

5380
5381
5382

DELDOS

JMP

GREAT

1219

A900

5383
5384

DDl

LDA

;SET FILE NOT EXISTS

121B

8D0E07

5385
5386

5387

WRTSCO

STA

DFSFLG

121E

A907

5388

LDA

#FMSORG/256 ;MOVE FMS START

1220

8D0503

5389

STA

DCBBUF+1

jADDR TO DCB

1223

A900

5390

LDA

#FMSORGS.255

1225

8D0403

5391
5392

STA

DCBBUF

1228

A900

5393

LDA

; CLEAR SECTOR NO TO

122ft

8D0A03

5394

STA

DCBSEC

122D

8D0B03

5395
5396

;

STA

DCBSEC+1

1230

EE0A03

5397

WRNBS

INC

DCBSEC

;INC SECTOR NO

1233

A201

5398

LDX

;GET DRIVE TYPE

1235

5399

SEC

1235

207207

5400
5401
5402

;

JSR

BSIOR

;D0 THE WRITE

1239

5403

CLC

123A

AD0403

5404

LDA

DCBBUF

;INC SECT ADDR

123:d

6980

5405

ADC

#128

123?

8D0403

5406

STA

DCBBUF

1242

AD0503

5407

LDA

DCBBUF+1

1245

6900

5408

ADC

♦

1247

8D0503

5409
5410

STA

DCBBUF+1

124A

AD0A03

5411

LDA

DCBSEC

;TEST FOR WRITE

1243

CD0107

5412

CMP

BRCNT

;0F ALL BOOT SECTORS

1253

D0DE

5413
5414

BNE

WRNBS

;BR NOT ALL

1252

5415
5416

RTS

1253

8C0F07

5417

SETDSO

STY

DELINK

;SET LINK START

125i5

8D1007

5418

STA

DFLINK+1

125'J

ADFE12

5419

LDA

DRVTYP

125(:

8D0E07

5420

STA

DFSFLG

125P

ACF812

5421

LDY

DRVMDL

WRITE DOS

1262 8C1107 5422

1265 D0B4 5423

5424

STY BLDISP
BNE DDl

;G0 WRITE SECTOR

WRITE DOS

1267

5425

.PAGE

1267 AD1207

5426

WD0

LDA

DFLADR

;MOVE PILE START ADDR

126A 8543

5427

STA

ZBUFP

;TO ZBUFP

126C AD1307

5428

LDA

DFLADR+1

126F 8544

5429
5430

STA

ZBUFP+1

1271 A000

5431

WDl

LDY

;MOVE 125

1273 B143

5432

WD 2

LDA

( ZBUFP ),Y

.•BYTES OF DOS

ATARI DOS 2.0S

12-'5

9147

5433

STA

(ZSBA),Y

1277

5434

INY

1278

CCF812

5435

cpy

DRVMDL

127B

90F6

5436

BCC

WD 2

127D

5437

TYA

127E

9D8713

5438
5439

STA

FCBDLN.X

12131

205707

5440

JSR

INCBA

12:34

CD0D07

5441

CMP

SASA+1

1237

900B

5442

BCC

WD 3

12:39

D00F

5443

BNE

WD4

12:3B

A543

5444

LDA

ZBUFP

12:3D

CD0C07

5445

CMP

SASA

1230

9002

5446

BCC

WD 3

1292

D006

5447
5448

BNE

WD4

1294

20940F

5449

WD 3

JSR

WRTNXS

1297

4C7112

5450
5451

JMP

WDl

129A

5452

WD4

RTS

5453

; AND

RETURN

5454

;T0 SECTOR BUFFER

;SET DATA LEN

INC ZBUFP BY 125
IF NOT END OR
PAST END OF DOS
THEN WRTNXS
ELSE
DONE

rWRITE NEXT SECTOR

; RETURN, CLOSE WILL WRITE
FINAL SECTOR

TEST DOS FILE NAME

129B

129B A00B
129D B95813
12A0 D9A812
12A3 D003
12A5 88
12A6 D0F5
12A8 60

12A9 44

12AA 4F

12AB 53

12 AC 20

1::AD 20

12AE 20

1:;AF 20

i:!B0 20
i:iBi 53
i;:b2 59

i;!B3 53
12B4 20

5455

5456 ;

5457 ; TSTDC

5458 ;

5459 TSTDOS
5460

5461 TDFl

5462

5463

5464

5465

5466 TDFR

5467 ;

5468 DFN

.PAGE "TEST DOS FILE NAME"

TEST FOR DOS SYS FILE NAME;

LDY
LDA
CMP
BNE
DEY
BNE
RTS

#11
FNAME-
DFN-1,
TDFR

TDFl

.BYTE "DOS

;LOOK AT 12 CHARS
1,Y rTEST DECODE FILENAME CHAR
Y ;WITH DOS FILENAME CHAR

rBR NOT MATCH

rBR IF MORE, ELSE RTN EQ

SYS "

5469

5470

; ERROR ROUTINES

5471

!B5

E649

5472

ERDBAD

INC

ERRNO

!B7

E649

5473

ERAPO

INC

ERRNO

!B9

E649

5474

ERRPOT

INC

ERRNO

IBB

E649

5475

ERFNF

INC

ERRNO

iBD

E649

5476

ERDFULL INC

ERRNO

IBF

E649

5477

ERDVDC

INC

ERRNO

!C1

E649

5478

ERFLOCK INC

ERRNO

!C3

E649

5479

ERRPDL

INC

ERRNO

!C5

E649

5480

ERRFN

INC

ERRNO

!C7

E649

5481

ERFNMM

INC

ERRNO

!C9

E649

5482

ERRSYS

INC

ERRNO

;BAD SECTOR AT FORMAT TIME
; ATTEMPT APPEND TO OLD TYPE

FILE
; POINT INVALID
;FILE NOT FOUND
; DIRECTORY FULL
; DEVICE COMMAND INVALID
;FILE LOCKED
.•POINT DATA LENGTH
;FILE NAME ERROR
;FILE NUMBER MISMATCH
r FATAL SYS DATA l/O ERROR

ATARI DOS 2.0S

12CB

E649

5483

ERRNSA

INC

ERRNO

i2cn

E649

5484

ERRNSB

INC

ERRNO

12CF

E649

5485
5486

ERRDNO

INC

ERRNO

12D1

A549

5487

LDA

ERRNO

12D3

AE0113

5488

RETURN

LDX

CURFCB

12D6

9D4303

5489

STA

ICSTA.X

12D9

AE0013

5490

LDX

ENTSTK

12DC

5491

TXS

12DD

AE0113

5492

LDX

CURFCB

12E0

5493

TAY

12E1

AD0813

5494

LDA

SVDBYT

;N0 SECTOR AVAIL

;N0 SECTOR BUFFERS AVAIL

; DRIVE NO ERROR

;GET ERROR NUMBER
;GET CUR FCB NO
;PUT IN FCB
;GET ENTRY STACK PTR
;AND RESTORE

;GET SAVED DATA BYTE

TEST DOS FILE NAME

12E4

5495
5496

RTS

12E5

AD0303

5497

ERRIO

LDA

DCBSTA

;GET I/O ERROR CODE

12E8

30E9

5498
5499

BMI

RETURN

12EA

AE0113

5500

FGREAT

LDX

CURFCB

12ED

20DE11

5501

JSR

FRESBUF

rFREE SECTOR BUFFER

12F0

A901

5502

GREAT

LDA

#01

;SET ALL OK

12F2

D0DF

5503

BNE

RETURN

12F4

A988

5504

ERREOF

LDA

#588

rSET EOF CODE

12F6

30DB

5505
5506

BMI

RETURN

MISC STORAGE

12F8

5507

.PAGE "MI

5508

5509

; MISC

NON

ZERO

5510

12Ffl

5511

DRVMDL

.BYTE

12F9

5512

.BYTE 125

12FA

5513

.BYTE 253

5514

;

12FI!

5515

DRVLBT

.BYTE

12FC

5516

.BYTE 127

i2Fn

5517

.BYTE 255

i2Fi:

5518

DRVTYP

*+l

i2Fr

5519

RETRY

*+l

130CI

5520

ENTSTK

*+l

1301

5521

CURFCB

* —

*+l

130:;

5522

DHOLES

*—

*+l

130;:

5523

DHOLED

*+l

130A

5524

DHFNUM

* —

*+l

1305

5525

CDIRD

*+l

1306

5526

CDIRS

*+l

1307

5527

SFNUM

*+l

130EI

5528

SVDBYT

*+l

1309'

5529

SVDl

*—

*+l

130A

5530

SVD2

*—

*+l

130E;

5531
5532

SVD3
EXTSW

*+l

130C

5533

TEMPI

*—

*+l

13011

5534

TEMP2

*+l

13011

5535

TEMP 3

*+l

130F

5536

TEMP4

*+l

i3iei

5537
5538

BURTYP

*ss

*+l

1311

5539

DRVTBL

It-

*+8

1319

5540

SECTBL

It—

*+16

1329

5541

DBUFAL

*—

*+8

1331

5542

DBUFAH

*+8

MAX DATA LEN
128 BYTE SECTOR
256 BYTE SECTOR

rDISPL TO LAST SECTOR BYTE

,•128 BYTE SECTOR

;256 BYTE SECTOR

; DRIVE TYPE

;l/0 RETRY COUNTER

; ENTRY STACK LEVEL

.■CURRENT FCB ( lOCB ALSO)

;DIR HOLE SECTOR

;DIR HOLE DISPL

DIR HOLE FILE NO

;CURRENT DIR DISPL

r CURRENT DIR SECTOR

;FILE NUMBER

; SAVED OUTPUT DATA BYTE

rSAVE DATA BYTES

.•FOR WRITE BURST

; TEMPI
;TEMP2
;TEMP3
;TEMP4
; BURST I/O TYPE

DRIVE TABLE

VTOC BUFFER
PTR FOR DRIVE N

ATARI DOS 2.0S

1339

5543

SABUFL

*+16

; SECTOR BUFFER

1349

5544

SABUFH

*+16

jFOR SECTOR N

1359

5545

FNAME

*+12

;FILE NAME

1365

5 546
5547

AFNAME

*—

*+12

jAUXILLARY FILE NAME

1371

5548
5549

MDRV

*+l

jMAX DR NO

1372

5550

;PUT ON SAME BOUNDRY AS
PRODUCTION

1372

5551

$1381

;VERSION

F]:LE CONTROL BLOCKS

13181

5552

.PAGE "FILE CONTROL BLOCKS"

5553

•

5554

; FILE

CONTROL BLOCK

5555

; ONE FILE

CONTROL BLOCK IS USED FOR EACH

5556

; OPEN

FILE. THE RELATIVE FCB USED

5557

; RELATES

DIRECTLY TO THE lOCB *

5558

r THAT

OPENED THE FILE.

THUS THERE ARE

5559

; 8 FCBS.

THE FCB ARE

(CONVIENTLY)

5560

; THE SAME

SIZE AS lOCBS. EACH FCB

5561

; CONTAINS

ALL THE INFORMATION REQUIRED

5562

; TO CONTROL THE PROCESSING ON AN

5563

r OPEN

FILE

5564

;

5565

FCB

1381

5566

FCBFNO

*+l ;

FILE # LEFT JUSTIFIED

1382

5567

FCBOTC

*+l

OPEN TYPE CODE

1383

5568

*+l ;

SPARE

1384

5569

FCBSLT

*—

*+i ;

FLAG FOR NEW SECTOR LEN 1

1385

5570

FCBFLG

*+l

WORKING FLAG

1386

5571

FCBMLN

It-

*+l

MAX SECTOR DATA LEN

1387

5572

FCBDLN

It—

*+l

CUR SECTOR BUF DATA LEN

1388

5573

FCBBUF

*—

*+l

SECTOR BUF NO

1389

5574

FCBCSN

*+2

CUR SECTOR #

138B

5575

FCBLSN

*—

*+2

LINK/ALLOCATE SECTOR #

138D

5576
5577

FCBSSN
FCBCRS

*—

*+2

CUR FILE RELATIVE SECTOR

138F

5578

FCBCNT

*+2

SECTOR COUNT

0310

5579
5580

FCBLEN

*-FCB

FCB LEN

1391

5581
5582

* =

FCBLEN*7+*

; ALLOCATE 7 MORE FCBS

5583

r OPEN

CODE BITS

5584

; USED

lOCB AUXl

5585

; - AND FCBOTC

5586

0004

5587

OPIN

$04

-INPUT

0008

5 588

OPOUT

$08

•OUTPUT

0002

5589

OPDIR

$02

jLIST DIRECTORY

0001

5590
5591

OPAPND

$01

; APPEND

0080

5592

FCBFAS

$80

; FCBFLG - ACQ SECTORS

0040

5593

FCBFSM

$40

; FCBFLG - SECTOR MODIFIED

FILE

DIRECTORY

1401

5594

.PAGE "FILE DIR

ECTORY"

5595

•

5596

,- DISK

FILE DIRECTORY

5597

; THE

FILE DIRECTORY

CCUPIES 8

5598

;CONSECTUIVE SECTORS S

TARTING AT THE

5599

,• CENTRAL

SECTOR+1 . E

ACH FILE DIRECTORY

5600

; SECTOR CONTAINS 8 EN

[TRIES . THERE

5601

; IS 1

ENTRY FOR EACH

NAMED FILE. THE

ATARI DOS 2.0S

0001

0003
0005
000D

0011?'

000(1
008 ei

004(1

0001

0020

000;

1401

5602
5603
5604
5605
5606
5607
5608
5609
5610
5611
5612
5613
5614
5615
5616
5617
5618
5619
5620
5621
5622
5623
5624
5625
5626

5627
5628
5629

THERE ARE A TOTAL OF 64 NAMED FILES
PER VOLUME

THE FILE NUMBER IS USED THROUGH THE
THE SYSTEM IS THE RELATIVE (TO ONE)
FILE DIRECTORY ENTRY NUMBER.

THE EQUATES BELOW ARE FOR A SINCE NAMED
FILE ENTRY

DFDFLl =

DFDCNT =

DFDSSN =

DFDPFN =

DFDXFN =

DFDELN =

;FLAG1 (1)

; SECTOR COUNTER (LOW)
; START SECTOR NO (2)
; PRIMARY FILE NAME (8)
rEXTENDED FILE NAME (4)
; ENTRY LENGTH

DFDFLl VALUE EQUATES

DFDEUU
DFDEDE
DFDINU
DFEXJUT
DFDLOC
DFDNLD

FILDIR *=

$80

$40

$01

$20

$02

*+256

; ENTRY UNUSED
r ENTRY DELETED
.•ENTRY IN USE
;FILE OPEN FOR OUTPUT
.•ENTRY LOCKED

;FILE HAS NEW TYPE SECTOR LEN
BYTE

r RESUME FILE DIR SPACE

VOLUME DIRECTORY

1501

0000

0001
0003

0005
000A

5630
5631
5632
5633
5634
5635
5636
5637
5638
5639
5640
5641
5642
5643
5644
5645
5646
5647
5648
5649
5650
5651
5652
5653
5654
5655
5656
5657

.PAGE "VOLUME DIRECTORY"

DISK VOLUME DIRECTORY

THE VOLUME DIRECTORY OCCUPIES THE CENTRAL

VOLUME SECTOR. THE VOLUME DIRECTORY

CONTAINS INFORMATION PERTAINING TO

THE ENTIRE DISKETTE VOLUME.

THE LABELS BELOW, MAP THE VOLUME
DIRECTORY SECTOR.

DVDTCD

; VOLUME DIRECTORY TYEP CODE )1)

USED TO DELINATE MAJOR (1)
FMS SYSTEM FORMAT CHANGES

DVDMSN =
DVDNSA =

DVDWRQ
DVDSMP

5
10

;MAX SECTOR NUMBER (1)
rNO SECTORS AVAIL

rWRITE REQUIRED
.•SECTOR MAP START

EACH BIT REPRESENTS A SECTOR

IF THE BIT IS ON THEN THE SECTOR

IS FREE AND AVAILABLE. IF THE

BIT IS OFF, THE SECTOR IS IN

USE OR BAD. THE MOST SIGNIFICANT

BIT OF THE FIRST BYTE IS SECTOR ZERO.

END OF FMS

1501

1501
1501

5658

5659 ;

5660 ENDFMS =

60 . END

PAGE "END OF FMS"

ATARI DOS 2.0S

EtID OF FMS

=0700

FMSORG

=0043

FMSZPG

=0340

lOCBORG

=0003

LMASK

=£1300

DCBORG

=E453

DHADR

=009B

EOL

=031A

DEVTAB

=CI020

ZICB

=02E7

LMADR

=1540

DUPINIT

=0102

STAR

=00DF

OSBTM

=0246

DSKTIM

=000F

TIMOUT

0340

lOCB

0340

ICHID

0341

ICDNO

0342

ICCOM

0343

ICSTA

0344

ICBAL

0345

ICBAH

0346

ICPUT

0348

ICBLL

0349

ICBLH

034A

ICAUXl

034B

ICAUX2

034C

ICAUX3

034D

ICAUX4

034E

ICAUX5

034F

ICAUX6

=0010

ICLEN

=0001

ICOIN

=0002

ICOOUT

=0003

ICIO

=0004

ICGBR

=0005

ICGTR

=0006

ICGBC

=0007

ICGTC

=0008

ICPBR

=£1009

ICPTR

=000A

ICPBC

=000B

ICPTC

=000C

ICCLOSE

=000D

ICSTAT

=000E

ICDDC

=000E

ICMAX

=000F

ICFREE

=£1001

ICSOK

=0002

ICSTR

=0003

ICSEOF

=0080

ICSBRK

=0081

ICSDNR

=0082

ICSNEP

=0083

ICSDER

=0084

ICSIVC

=0085

ICSNOP

=0086

ICSIVN

=0087

ICSWPC

=0021

ICDNOZ

=0028

ICBLLZ

=0029

ICBLHZ

=0024

ICBALZ

=0025

ICBAHZ

=0022

ICCOMZ

=0026

ICPUTZ

0300

DCB

0300

DCBSBI

0301

DCBDRV

0302

DCBCMD

0303

DCBSTA

0304

DCBBUF

0306

DCBTO

0308

DCBCNT

030A

DCBSEC

=0052

DCBCRS

=0050

DCBCWS

=005 3

DCBCST

=0021

DCBCFD

=0001

DCBSOK

=0081

DCBDNR

=0082

DCBCNR

=0083

DCBDER

=0084

DCBIVC

=£1087

DCBWPR

0043

ZBUFP

0045

ZDRVA

0047

ZSBA

0049

errno

0700

BFLG

0701

BRCNT

0702

BLDADR

0704

BINTADR

0706

BCONT

0714

XBCONT

0709

SABYTE

070A

DRVBYT

070B

SAFBFW

070C

SASA

=1501

ENDFMS

070E

DFSFLG

070F

DFLINK

0711

BLDISP

0712

DFLADR

07CB

DFMSDH

074F

BFAIL

072F

XBCl

=076C

BSIO

0753

BGOOD

0757

INCBA

0754

XBRTN

0772

BSIOR

077C

DSIOl

0786

DSI02

12FF

RETRY

079C

DSI03

07A2

DSI04

07C4

DSI05

07BE

STRTYP

1301

CURFCB

08AB

DFMOPN

0B15

DFMCLS

=0ABF

DFMGET

09CC

DFMPUT

0B01

DFMSTA

0BA7

DFMDDC

=07E0

DINIT

130C

TEMPI

07P2

DIA

130D

TEMP2

0807

DIHAVE

1311

DRVTBL

1329

DBUFAL

1331

DBUFAH

083D

DIDDEC

=0005

DVDWRQ

0823

DI256

0870

DINCBP

0845

DINXTS

084B

DISETS

1319

sectbl

08 5E

DISNI

1339

SABUFL

1349

SABUFH

=087E

CLRFCB

0882

CFCBX

1381

FCB

088A

ADIl

089B

ADI2

1164

SETUP

0E9E

FNDCODE

1382

FCBOTC

=0002

OPDIR

08BE

OPNl

0DAD

LISTDIR

0F21

SPDIR

=0004

OPIN

=08D8

DFOIN

=0008

OPOUT

=0911

DFOOUT

=08DD

DFOUPD

=0001

OPAPND

=fl8EC

DFOAPN

12BF

ERDVDC

08E9

OPNERl

=08E3

DFOUI

0CAC

TSTLOCK

09AE

DFRDSU

12F0

GREAT

12BB

ERFNF

1305

CDIRD

1401

FILDIR

=0000

DFDFLl

=0002

DFDNLD

090E

APOER

10BF

OPVTOC

].106

GETSECTOR

138D

FCBSSN

13aB

FCBLSN

=097C

DHF0X2

].2B7

ERAPO

=091D

DFOXl

0C53

XDEL0

=0948

OPNIA

1302

DHOLES

0992

0PNER2

1306

CDIRS

10eE

RDDIR

:.303

DHOLE D

1304

DHFNUM

1307

SFNUM

093E

OPNIB

=0005

DFDPFN

=0003

DFDSSN

=0040

DFDINU

=0001

DFDOUT

=0001

DFDCNT

0966

0PN2

1359

FNAME

=0970

0PN2A

1071

WRTDIR

=0995

SETFCB

0FE2

WRTN6

0982

0PN3

=0080

FCBFAS

1385

FCBFLG

129B

TSTDOS

=098F

DHF0X3

].20A

WRTDOS

12BD

ERDFULL

099A

OPNFl

1381

FCBFNO

1387

FCBDLN

138F

FCBCNT

1384

FCBSLT

=1017

RDNSO

1308

SVDBYT

1300

ENTSTK

09E5

FRMCIO

0A19

PUTER

1386

FCBMLN

0A06

PUTl

0F94

WRTNXS

0A1C

PEOF

OAIF

WTBUR

=0040

FCBFSM

12F4

ERREOF

0A4A

NOBURST

0A28

TBURST

0A26

RTBUR

1310

BURTYP

=0AAE

TBLEN

()A3E

NXTBUR

0A4C

WRBUR

100F

RDNXTS

0A7B

BBINC

=I)A9D

BUREOF

12F8

DRVMDL

1309

SVDl

130A

SVD2

:L30B

SVD3

1388

FCBBUF

11D0

SSBA

0AAC

BURST

:l2pe

DRVTYP

0AB9

TBL256

0ACC

GETl

0DB9

GDCHAR

UADF

GET 2

=0ADC

GEOF

=0AEA

EFLOOK

0AFE

GET3

:L2D3

RETURN

0B12

SFNF

0B6D

CLDONE

=0B75

CLUPDT

IJFAB

WRTLSEC

=0B80

RRDIR

0B50

CLOUT

0B3C

APPl

ATi\RI DOS 2.0S

0FB3

WRTN2

1095

WRTVTOC

12EA

FGREAT

0FF8

WRCSIO

0B9B

FNSHFT

0B9D

FNSHFl

0B9F

FNSHF2

0BD6

XFV

■0027

MAXDDC

0BD3

DVDCER

0BC5

DVDCVT

0BD9

XRENAME

0C32

XDELETE

0C7C

XLOCK

0C83

XONLOCK

0CBA

XPOINT

0D03

XNOTE

0D18

XFORMAT

0BE7

XRNl

0BF2

XRNl A

1219

DELDOS

0EB4

FNDCNX

0C0C

XRNIB

1253

SETDSO

0C11

XRN2

0C1B

XRN3

0F31

CSFDIR

0C79

DFNF

=0C3A

XDELX

0C45

XDELY

0C45

XDEL3

0C56

XDELl

=008 C!l

DFDEDE

=0C6C

XDEL2A

0C67

XDEL2

=0C72

XDEL4

10C5

FRESECT

=0020

DFDLOC

130F

TEMP4

0C88

XLCOM

0C93

XLCl

0CB7

TLF

12C1

ERFLOCK

0D00

PERRl

1389

FCBCSN

0CCF

XPl

0CED

XP2

=0CDC

XPl A

=0CF7

XPERR

0CFA

XP3

12C3

ERRPDL

12B9

ERRPOT

0D52

XF0

0D4F

XFERR

=0D3D

TSTFMT

0D4C

XFBAD

12B5

ERDBAD

0D55

XFl

=000A

DVDSMP

0D76

XF2

0D94

XF3

0D9F

XF4

0DE3

LDENTl

0DE9

LDCNT

0E11

LDDONE

0DD6

GDCRTN

0DD9

LDENT

0E21

FDENT

108B

RDVTOC

=0003

DVDNSA

0E57

CVDX

=000D

FSCML

0DFD

MVFSCM

0E14

FSCM

0E67

CVDY

0E35

LDl

0E3B

LD2

0E71

CVDIGIT

0E8D

STDIGIT

130E

TEMP3

0E76

CVDl

0EAA

FD0A

0F07

FNDERR

0EB3

FD0B

0EB8

FD0

130C

EXTSW

0EC3

FDl

0ED5

FD3

0ECR

FD2

0F0A

FDSCHAR

0F03

FDEND

0EE5

FD4

0EFD

FD6

0EF1

FD5

12C5

ERRFN

0F1B

FDSC2

0F15

FDSCl

=0010

DFDELN

0F4D

SFD2

0F48

SFDl

0F90

SDRTN

0F73

SPDSH

0F5E

SFD3

0F6A

SFD4

0FBA

SFDSHl

0FA8

WRTNl

0FA5

WRUl

0FC9

WRNERR

0FAE

WRTLSl

12FB

DRVLBT

0FDA

WRTN5

1002

MVLSN

0FF6

WRNRTS

0FF9

RWCSIO

11F7

DSIO

1021

RDNSl

105P

RDIOER

=1062

RDFNMM

1054

RDNS3

1051

RONS 2

12E5

ERRIO

106C

RDDELE

12C7

ERFNMM

1072

DIRIO

10AB

DSYSIO

1092

RDVGO

109C

VTIO

1095

WRVTOC

10AC

DSYSIA

10B5

DSIOER

10BC

DEAD

12C9

ERRSYS

=1105

FSRTS

10D1

FSl

10DD

FS2

10E5

FS3

1108

GSl

1161

GSERR

112D

GS2

1134

GS3

1148

GS4

12CB

ERRNSA

IIDB

DERRl

llAl

GSBl

llAE

GSB4

11A6

GSB2

llAB

GSB3

12CD

ERRNSB

11C4

GSB5

12CF

ERRDNO

=11DE

FRESBUF

11F6

FSBR

1267

WD0

121B

DDl

121E

WRTSCO

1230

WRNBS

1271

WDl

1273

WD 2

1294

WD 3

129A

WP4

129D

TDFl

12A9

DFN

12A8

TDFR

1365

AFNAME

1371

MDRV

=1372

138F

FCBCRS

=0010

FCBLEN

=000D

DFDXFN

=0000

DFDEUU

=0000

DVDTCD

=0001

DVDMSN

100

Appendix A

AN
INTERMEDIATE
USER'S GUIDE
TO THIS BOOK

If you are familiar with machine language, commented source code,
and hexadecimal numbers, you probably won't need to read this
appendix. On the other hand, if you don't know or are new to machine
language - perhaps some of the information here will help.

A knowledge of machine language is important to grasping the
sense of the DOS since it is written in machine language. However,
we will briefly cover some of the fundamentals, as they relate to the
book, in the hope that this might be a starting point. One of the
functions of this book is to reveal the inner workings of Atari DOS. A
benerit of knowing how it works is that you are able to change it to
suit yourself, to customize it.

First we'll examine the meaning of the various fields of information
whicli are in the source code (page 59 on). Then, after a brief look at
how ro deal with hexadecimal numbers, we can make a modification
to D(DS step-by-step to show how it's done.

The book is divided into two sections: roughly the first half is a
series of descriptions of the major subroutines of the disk operating
system. The latter half is a commented source code of the DOS. In order
to better understand what you can accomplish with all this information,
we can set up a problem and solve it using the book.

Whoit's "Commented Source Code"?

We'll change the DOS so that we could type in a disk command using
lowercase letters. Unfortunately, the D: must be in uppercase, the
program which makes this decision is in ROM and we can't get at it
and change it. The rest of the command can be in lowercase, though,
after we make our change to the DOS in RAM. After fixing it, any
routine that uses the disk will accept lowercase as in D: open.

102

APPENDIX A

Before getting into the details of the modification there is some
important preliminary information. What, for example, is "commented
source code?"

Machine language differs in several respects from BASIC. When
you write a program in BASIC, you never see how it looks to the
computer. Instead you see something like this:

10 FORI = lTO100
20 NEXT 1

This delay loop just creates a brief pause in a program. If you
RUN the above, the computer handles the problem of translating the
BASIC words into machine language. Anything the computer does
must be translated into machine language (ML). Translating (or
interpreting) a BASIC program takes place during the RUN of the
program - that's why BASIC is so slow compared to ML.

By contrast, ML is translated before it is RUN. Programming ML
is done in two stages: 1. writing the source code and then 2. assembling
it into object code. The computer does most of the drudgery of this
because most ML is written by using a program called an assembler
which handles many of the details. Some assemblers are so complex
ttiat using them can seem almost like programming in BASIC.

Here is how you might program the above example delay loop
when using an assembler:

1 000 LDY #64 ; SET COUNTER TO 1 00

1001 LOOP DEY

1002 BNE LOOP

Probably the most peculiar thing about this, to the beginner, is
how 64 stands for 100 (it's hex, we'll get to it in a minute). The line
nambers could be BASIC, but the instructions are 6502 mnemonics
(memory aids). LDY means to load the Y register with 100 (decimal).
The next line is named (labelled) "loop" because assemblers don't say
CiOTO 1001. Instead, they use convenient names. In any event, the
Y register is decremented by DEY, it's lowered by one. So each time
the program cycles through the LOOP address, it will lower the counter
one. Finally, the instruction at 1002 says. Branch if Not Equal (to
zero). In other words, GOTO LOOP if Y hasn't yet counted down to
zero. When Y reaches zero, the program will continue on, following
whatever instruction is in line 1003.

After the above program is written, though, it still cannot be
BUN. There is the second step, the creation of object code
((Executable), the assembly process.

You tell the assembler to assemble this program. The result of

103

APIPENDIXA

that is an additional two "fields" (zones). Above, we have five fields:
line number, label, mnemonic (instruction), operand (the #64), and
a comment field which is the equivalent of BASIC REM statements.
There will soon be a total of seven fields.

After assembly, the two new fields are the addresses and the
object code (expressed as hex bytes). By the way, BASIC always
assigns its programs a starting address in memory, but, in ML, the
programmer must make this known to the assembler. It's not the
computer's decision. Assume the computer were told to assemble the
above example at address $2000 (this would be 8192, in decimal).
The dollar sign means that a number is a hex number. The labels,
mnemonics, and operands would be translated into object code and
put into the computer's memory. As you'll see in the second half of
this iDook, a printout of completed assembly looks like this:

200C AOOO 1000 LDY #64 ; SET COUNTER TO 100

2002 88 1001 LOOP DEY

2003 DOFF 1002 BNE LOOP

Hex

Before concluding this brief overview of some fundamentals of machine
language, we should explain how to read the numbers in the source
code listings.

100 DIM H$(23) ,N$(9) :OPEN#1,4,0,"K:"

130 GRAPHICS

140 PRINT "PLEASE CHOOSE:

150 PRINT "1 - Input HEX & get decimal back

160 PRINT "2 - Input DECIMAL to get hex bac

k."
170 PRINT:PRINT "==>"; :GET#1 ,K
180 IF K<49 OR K>50 THEN 170
190 PRINT CHR$(K):ON K-48 GOTO 300,400
300 H$="@ABCDEFGHI! ! ! ! ! ! IJKLMNO"
310 PRINT "HEX";:INPUT N$:N=0
320 FOR 1=1 TO LEN(N$)

330 N=N*16+ASC(H$(ASC(N$(I))-47))-64:NEXT I

350 PRINT "$";N$;"=";N:PRINT:PRINT:GOTO 140

400 H$="0123456789ABCDEF"

410 PRINT "DECIMAL"; : INPUT N:M=4096

4 20 PRINT N;"=$";

104

APPENDIX A

430 FOR 1=1 TO 4:J=INT{N/M)

440 PRINT H$(J+1,J+1) ; :N=N-M*J:M=M/16

450 NEXT I:PRINT:PRINT:GOTO 140

This program will turn a decimal number into hex or vice versa.
Hexadecimal is a base 16 number system, where decimal is base ten.
This means that you count from zero to fifteen before going to the
n(!xt column. For example, you count up zero one two. . .until you
reach nine in decimal. Then you go to the next column and have a
one-zero (10) to show that there is one in the "ten's column" and zero
ir the "one's column. "

In hex, what was a "ten's column" becomes a "sixteen's column."
In other words, the symbol "10" means that there is one sixteen and
zero "ones." So, the decimal number 17 would be written in hex, as
$11 (one sixteen plus one one). The decimal number 15 would, in
hex, be $0F. After nine, we run out of digits, so the first few letters of
the alphabet are used: A= 10, B= 11, C= 12, D= 13, E= 14, and
F=15.

This explains how to "read" hex numbers if you don't want the
pirogram above to do it for you. The number $64 is decimal 100 because
there are six 16's and four one's. 6 X 16 4- 4 = 100.

Addresses can be larger than two digits, up to a maximum of
four. You might see an address such as $1 1F7 in the listings. The third
column is the 256's and the fourth column is the 4096's. So to find
out what this address is in decimal, you can multiply 7X1, 15X16,
1 X 256, and 1 X 4096. And add them all together.

A quicker way is to find out the first two, (15x16 + 7 = 247) and
tlien multiply the second two by 256. It comes out the same. The
second two would be $ 1 1 ( 1 7 in decimal) so 1 7 x 256 + 247 = 4599. It
might be easier to just use the BASIC program to make the translations
until hex becomes more familiar.

Making A Modification

Now that you have the entire source listing of EXDS 2. OS, you can
customize it to fit your needs.

You may have felt restricted by the limitations on file names. A
file name can consist of eleven characters: up to eight characters plus
an optional three-character extension. The first character must be
from A-Z; subsequent characters can be from A-Z or 0-9. That's it.
f >]o punctuation. No imbedded spaces. No lowercase.

By changing only two locations in the file name decode section
of DOS, many more characters are permitted. We will modify DOS to

105

APPENDIX A

accept any ASCII characters in a file name except character graphics
and inverse video. Additionally, the filename can start with a number
(e.g. "D:3-D"). Unfortunately, there is no foolproof way to allow
imbe^dded spaces such as "D:TIME OUT".

The following fragment of code checks to see that a character of
the file name falls in the range of A-Z. If the character is less than
(cany clear) 65 [ASC("A")] or greater than or equal to (carry set) 91
[ASCC'Z") + 1], then the test fails. All we do is change the check for
"A" to a check for "!" (its number in the code is one greater than
"space"), and the check for "Z" + 1 to "z" + 1 (lowercase z).

Included in this range of 90 characters are the numbers (48-57)
and all punctuation. Since we start with 33, "space" is excluded. It is
possible to permit imbedded spaces, but the file would then be
inaccessible in certain situations where a space is used as a delimiter.
You i:an allow it at your discretion, or even permit the entire (almost)
AT/iSCII character set to be used by changing the limits to
and 155.

CMP #'A

BCC FD5

CMP #$5B

BCC FD6
We change this to:

CMP #'!

BCC FD5

CMP #$7B

BCC FD6

The changes can be made in BASIC with POKE 38 18, 33: POKE
3822, 123 or change hex locations $OEEA to $21 and $OEEE to $7B.
The section of code we're modifying is located between source line
numbers 4072 through 4193. Remember to rewrite the modified DOS
to disk with WRITE DOS FILES (Menu selection "H") if you want
your change to be permanent.

Other equally simple changes are also possible. You could change
the wild-card character ("*") to any other character by changing
location $0EC7 to the desired character. A more ambitious task
would be to increase the maximum file name length.

This brings up a final point - software compatibility. For example,
if you changed the wild card character to "@," you couldn't run any
previ.3us programs that assume "*" as the wild card character. Our
change is less dangerous - if you allow lowercase file names, the
unmodified DOS won't be able to access it, although it will look fine
on the directory. This change has not been exhaustively tested for

106

APPENDIX A

conflicts, so we can't guarantee its usage. Nevertheless, it seems quite
useful and shows that some customizing can be accomplished with a
few simple changes.

When experimenting, always keep a backup copy of your valuable
disks in case something should go awry.

100 REM CHANGE DOS PROGRAM

110 REM FOR DOS 2.0S ONLY

120 REM CHANGE LOW RANGE CHECK FROM

130 REM 65 TO 33. THIS ALLOWS

140 REM ANY CHARACTER (EXCEPT

150 REM GRAPHICS AND INVERSE VIDEO)

160 REM TO START A FILENAME, INSTEAD

170 REM OF ONLY A THROUGH Z.

180 REM 0EE9 C941 CMP #'A

190 REM 0EE9 C921 CMP #'!

200 POKE 3818,33

210 REM CHANGE HIGH RANGE TO EXTEND

220 REM UP TO ASCII "z"

230 REM (LOWERCASE Z)

240 REM 0EED C95B CMP #$5B

250 REM 0EED C97B CMP #$7B

260 REM POKE 3822,123

270 REM NO NEED TO CHANGE NUMERIC

280 REM CHECK SINCE IT IS NO

290 REM LONGER EXECUTED, THANKS

300 REM TO THE ABOVE CODE.

Siome Cautions

C^^are is necessary when making customizations. Only make the changes
to a copy of your EXDS - not the original "system master." (You
shouldn't be able to do this anyway, since the disk is "write-protected, "
but better safe than sorry. ) Remember that any files SAVEd with your
custom EXDS will probably not be compatible with the original,
unchanged DOS. Alternation of the DOS can have unpredictable
effects; we urge caution and cannot accept any liability for software or
hardware damage incurred through the use of this book.

Things To Looi( Out For

These modifications could make a customized DOS incompatible with
the original, unmodified DOS 2. OS:

1) File name changes (such as allowing lowercase, or increasing

107

APPENDIX A

the length)

2) Changes to DOS file stnicture (such as using a different
"linking" system)

3) Removing error-checks. These built-in traps insure disk
integrity and reliability. When you alter one, you could risk
muddling one or more files. For example, if you allow an automatic
"wild-card" feature, where an asterisk is assumed at the end of a
file, it could cause havoc when performing a SCRATCH,
RENAME, or UPDATE operation. Another example is removing
some of the qualifications for "burst- I/O." Remember that a lot
of thought went into each design consideration.

Keeping these suggestions in mind, here are some ideas for
modifications. You may need to type in and re-assemble (with your
insertions) the entire DOS when making certain modifications.

1 ) Adding a STATUS check before a disk access. Have you ever
noticed how long the drive will grind away when no disk is
inserted? You can query the disk for its status, and even add a
"Drive not ready" error message if the drive door is not closed or
a disk is not inserted. Check your DOS manual for details.

2) Adding Disk Utility commands. These would be additional
functions performed by the FMS, keyed to the "special command. "
Some of the tasks performed by the Disk Utility Package could be
a part of the DOS kemal, such as LOAD and SAVE binary files.
You could even implement new commands such as "relative file"
support, where you only give the DOS a "record number" to
randomly access a file. The file could be divided into records of
any length.

3) Allocate more sectors for the directory, thereby extending
the maximum amount of directory entries.

4) Add a disk name and/or disk I.D. number (serial number?) to
the disk (maybe on sector 720). It could even print out with the
directory.

5) Given the extra "unused" bytes in the file name, add a byte
for file type, such as program, data, object code, etc. , and have it
printed out with the directory, making it easy to identify files
without having to use the extension. This would be hard to
interface with software, however.

Remember that some of this is risky business. Keep backup disks
for any disk you are "experimenting" with. That way, you should lose
no important files.

The publishers and authors of this book disclaim any responsibility for errors or
problems caused by modification of Atari DOS 2. OS.

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